Correction or disambiguation of A100796 Topological equivalence class of numeral representing n.

[Maximilian Hasler]

> which font is used. Letter topology is of practical relevance in
> stencil typography: The font Braggadocio, for instance, can be > cut out of a plane without falling apart.

at first glance this seems to indicate that all letters are
topologically equivalent to a dash (not to say: a dot)

M.H.



zak seidov <zakseidov at yahoo.com> wrote:
:Neil, Rick , seqfans,
:My numbers are:
:1, 3, 9, 17, 40, 56, 90, 114, 164, 253, 289, 404, 484,
:533, 634, 783, 973,1031, 1233, 1373, 1452, 1683, 1842,
:2112, 2483, 2676, 2772, 2938, 3024, 3184, 
:3795, 3955, 4195, 4290, 4701, 4792, 5063, 5348, 5515,
:5773, 6043, 6124, 6592, 6674, 6842, 6926, 7460, 8036,
:8230, 8329, 8535, 8829, 8926, 9426, 9725, 
:10028, 10307, 10411, 10707, 10909
:and they  differ from A128301 starting with 2772 on.
:Can anyone please check/get correct results,
:thanks,
:Zak
:
:%I A128301
:%S A128301
:1,3,9,17,40,56,90,114,164,253,289,404,484,533,634,783,973,1031,1233,1373,1452,1683,1842,2112,2483,2676,2779,2995,3108,3320,4124,4384,4775,4926,5593,5741,6172,6644,6962,7448,7955,8108,8978,9147,9512,9697,10842
:%N A128301 Indices of squares (of primes) in the
:semiprimes.
:%C A128301 A001358(a(n)) = A001248(n) = A000040(n)^2.
:%e A128301 a(4) = 17 as 49=7^2=prime(4)^2, the fourth
:square in the semiprimes, is the seventeenth 
:               semiprime.
:%Y A128301 Cf. A128302, A001358, A001248.
:%Y A128301 Adjacent sequences: A128298 A128299 A128300
:this_sequence A128302 A128303 A128304
:%Y A128301 Sequence in context: A123325 A116688
:A011755 this_sequence A018307 A108050 A009211
:%K A128301 nonn
:%O A128301 1,2
:%A A128301 Rick L. Shepherd
:(rshepherd2(AT)hotmail.com), Feb 25 2007

The following code agrees with the existing values, not with yours:
perl -MMath::Pari=factorint,PARI -wle 'my $c = 0; my $s = PARI 1; while (1) { ++$s; my($sp, $si) = @{factorint($s)}; next if @$sp > 2; next if $si->[0] + (@$si > 1 ? $si->[1] : 0) != 2; ++$c; print "$s => $c" if @$sp == 1}'

Semiprimes between 10201 (at index 2676) and 10609 (at index 2779) are:
2676:                                    (10201)10202 10207 10213
2680: 10214 10217 10219 10221 10226 10229 10231 10237 10238 10239
2690: 10249 10261 10265 10277 10279 10291 10294 10297 10299 10306
2700: 10307 10315 10319 10327 10334 10342 10345 10347 10349 10351
2710: 10358 10361 10363 10367 10371 10378 10379 10381 10383 10389
2720: 10393 10394 10397 10401 10403 10405 10407 10409 10411 10415
2730: 10417 10418 10421 10423 10435 10441 10445 10447 10451 10454
2740: 10462 10466 10471 10473 10474 10481 10483 10489 10493 10495
2750: 10497 10511 10517 10519 10522 10523 10533 10537 10541 10543
2760: 10546 10547 10551 10553 10555 10558 10561 10562 10565 10573
2770: 10577 10579 10581 10583 10587 10594 10599 10603 10606(10609)

Hugo