%I #32 Sep 08 2022 08:46:13
%S 1,13,3133,204525373,878416384666881853,
%T 16203922234330403022943873881213226813,
%U 5513909011300771210646237381366090850171917477741023928710521838825947516733
%N a(n) = (2^(2^(n+1)) + 2^(2^n) + 1)/21.
%F a(n) = A001576(2^n)/21. - _Michel Marcus_, Aug 14 2015
%e a(2) = (2^(2^(2+1)) + 2^(2^2) + 1)/21 = 13.
%t Table[(2^(2^(n + 1)) + 2^(2^n) + 1)/21, {n, 1, 10}] (* _Vincenzo Librandi_, Aug 08 2015 *)
%o (PARI) first(m)=my(v=vector(m,t,(2^(2^(t+1))+2^(2^t)+1)/21));v; /* _Anders Hellström_, Aug 07 2015 */
%o (Magma) [(2^(2^(n+1)) + 2^(2^n) + 1)/21: n in [1..10]]; // _Vincenzo Librandi_, Aug 08 2015
%Y Cf. A001576 (1^n + 2^n + 4^n).
%K nonn,easy
%O 1,2
%A _Marco RipĂ _, Aug 07 2015
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