This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A257391 #26 Jul 17 2024 13:30:23
%S A257391 29120,32537600,34093383680,36011213418659840,36888985097480437760,
%T A257391 38685331082014736871587840,39614005699412557795646504960,
%U A257391 41538369916519054182462860998737920,44601490313984496701256699111250939955118080,45671926145323068271210017365594287580527984640
%N A257391 Numbers of the form 4^p*(4^p+1)*(2^p-1) with p an odd prime.
%C A257391 5 divides (4^m+1) for odd m, so every term in this sequence is a multiple of 5 (A008587).
%C A257391 A064487(k) = 4^(2k+1)*(4^(2k+1)+1)*(2^(2k+1)-1), so this sequence is a subsequence of A064487.
%C A257391 Every non-solvable number (A056866) is divisible by 12 or 20. All non-solvable numbers not divisible by 12 (A008594) are divisible by a member of this sequence. In particular, every primitive non-solvable number (A257146) not divisible by 12 is in this sequence.
%C A257391 All terms are divisible by 320 and have at least 4 distinct prime factors. - _Jianing Song_, Apr 04 2022
%D A257391 See A056866 and A064487 for references.
%H A257391 Danny Rorabaugh, <a href="/A257391/b257391.txt">Table of n, a(n) for n = 1..100</a>
%F A257391 a(n) = 4^p*(4^p+1)*(2^p-1) where p = A065091(n) = A000040(n+1).
%t A257391 Table[4^p (4^p+1)(2^p-1),{p,Prime[Range[2,20]]}] (* _Harvey P. Dale_, Jul 17 2024 *)
%o A257391 (Sage) [4^nth_prime(n)*(4^nth_prime(n)+1)*(2^nth_prime(n)-1) for n in range(2,12)]
%o A257391 (PARI) a(n)=my(p=prime(n+1)); 4^p*(4^p+1)*(2^p-1) \\ _Charles R Greathouse IV_, Apr 21 2015
%Y A257391 Subsequence of A008587, A008602, A056866, and A064487.
%K A257391 nonn,easy
%O A257391 1,1
%A A257391 _Danny Rorabaugh_, Apr 21 2015