A357751 a(n) is the least perfect power > 2^n.

4, 4, 8, 9, 25, 36, 81, 144, 289, 529, 1089, 2116, 4225, 8281, 16641, 33124, 66049, 131769, 263169, 525625, 1050625, 2099601, 4198401, 8392609, 16785409, 33558849, 67125249, 134235396, 268468225, 536895241, 1073807361, 2147488281, 4295098369, 8589953124, 17180131329, 34359812496

Offset: 0

Author

Hugo Pfoertner, Oct 12 2022

Keywords

• nonn
• easy

Links

• David A. Corneth, Table of n, a(n) for n = 0..3321

Crossrefs

Cf. A000079, A001597, A357752.

Programs

Mathematica

pwQ[n_] := n == 1 || GCD @@ (Last /@ FactorInteger@n) > 1; a[n_] := Block[{t = 2^n + 1}, While[! pwQ@t, t++]; t]; a /@ Range[0, 30] (* Giovanni Resta, Oct 12 2022 *)

PARI

for (n=0, 35, for (k=2^n+1, oo, if(ispower(k), print1(k,", "); break)))

PARI

a(n) = { if(n < 2, return(4)); my(p2 = 1<David A. Corneth, Oct 12 2022