[seqfan] Re: A173088 edited

[Klaus Brockhaus]

Obviously my program was not correct; the corrected version (below) 
gives the original
sequence except for a(5) = 18 instead of 17 and a few other terms.

Klaus

--------------------------------------------------------------
T:=[ k: k in [1..3000] | IsPrime(6*k-1) and IsPrime(6*k+1) ]; //A002822
[ p: p in T | IsPrime(6*p-1) and IsPrime(6*p+1) and IsPrime(6*(p+5)-1) 
and IsPrime(6*(p+5)+1) ];

Magma V2.16-6     Tue Mar  2 2010 04:20:10    [Seed = 3676006339]
   -------------------------------------

[ 2, 5, 7, 12, 18, 25, 33, 40, 47, 72, 95, 138, 170, 172, 177, 215, 242, 
278,
333, 347, 352, 373, 385, 443, 495, 550, 555, 560, 588, 637, 670, 688, 
705, 707,
753, 975, 1045, 1110, 1127, 1243, 1260, 1433, 1495, 1502, 1572, 1668, 1673,
1712, 1717, 1738, 1750, 1810, 1990, 2007, 2280, 2282, 2317, 2427, 2555, 
2898,
2993 ]

Total time: 0.300 seconds, Total memory usage: 9.03MB


Klaus Brockhaus schrieb:
> Could some seqfan please check this?
>
> Thanks and regards
>                       Klaus
>
> Edited version:
>
> %I A173088
> %S A173088 
> 2,4,5,7,9,11,14,16,18,22,25,32,35,36,38,43,47,52,60,62,64,67,69,74,80,
> %T A173088 
> 86,87,88,93,99,104,107,110,111,117,140,146,152,155,167,170,183,188,190,
> %U A173088 
> 196,205,206,210,211,213,215,218,233,235,251,252,258,268,275,301,313
> %N A173088 Numbers n such that (6*p-1, 6*p+1) and (6*(p+5)-1, 6*(p+5)+1) 
> are twin prime pairs, where p is A002822(n).
> %e A173088 A002822(2) = 2. 2 is in the sequence because 
> 6*(A002822(2)+0)-1 = 6*2-1 = 12-1 = 11 is prime, 6*(A002822(2)+0)+1 = 
> 6*2-1 = 12+1 = 13 is prime, 6*(A002822(2)+5)-1 = 6*7-1 = 42-1 = 41 is 
> prime and 6*(A002822(2)+5)+1 = 6*7+1 = 42+1 = 43 is prime.
> %e A173088 A002822(4) = 5. 4 is in the sequence because 
> 6*(A002822(4)+0)-1 = 6*5-1 = 30-1 = 29 is prime, 6*(A002822(4)+0)+1 = 
> 6*5+1 = 30+1 = 31 is prime, 6*(A002822(2)+5)-1 = 6*10-1 = 60-1 = 59 is 
> prime and 6*(A002822(2)+5)+1 = 6*10+1 = 60+1 = 61 is prime.
> %Y A173088 Cf. A002822 (numbers n such that 6*n-1, 6*n+1 are twin primes).
> %K A173088 nonn,new
> %O A173088 1,1
>
>