[seqfan] Re: a(n) is tau[a(n)+a(n+1)]

Richard Mathar mathar at strw.leidenuniv.nl
Tue May 25 18:17:15 CEST 2010

http://list.seqfan.eu/pipermail/seqfan/2010-May/004743.html asks

njas> ...
njas> and apologies.  Would someone kindly submit the
njas> (correct versions of) these sequences?

This one was approximately

%I A000001
%S A000001 2,3,6,12,48,2472,17569637319163259504744306426508888
%N A000001 Increasing sequence with a(1)=2 and a(n) = tau(a(n)+a(n+1)).
%C A000001 The algorithm is: obtain the smallest number with a(n) divisors, for example
%C A000001 via A005179 - if this equals a(n) take the next larger candidate, and
%C A000001 subtract a(n) to compute a(n+1).
%C A000001 a(8) is (2^1567597904993153060737357818210 * 3^466 * 5^2 * 7 * 11 * 13) - 17569637319163259504744306426508888,
%C A000001 approximately 4.676024*10^471893990542954871479908400227 [R. Munafo (mrob27(AT)gmail.com], May 18 2010
%K A000001 nonn
%F A000001 a(n+1)= A000005(a(n)+a(n+1)).
%O A000001 1,1
%A A000001 Eric Angelini (Eric.Angelini(AT)kntv.be), May 18 2010
%E A000001 a(7) from M. F. Hasler (Maximilian.Hasler(AT)gmail.com), May 18 2010

%I A000002
%S A000002 0,0,1,2,11,6,57,16,27,38,1013,48,4083,178,129,104,65519,162,262125,220,
%T A000002 555,3050,4194281,336,1271,12262,873,932,268435427,690,1073741793,808,9183,
%U A000002 196574,5149,1224,68719476699,786394,36825,1640,1099511627735,2838
%N A000002 A005179(n) - n.
%K A000002 nonn
%O A000002 1,4
%A A000002 M. F. Hasler (Maximilian.Hasler(AT)gmail.com), May 18 2010

I don't know if anyone has already submitted anything equivalent to these; I haven't.
Richard Mathar

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