A068315 For numbers k such that A025474(k) > 1 and A025474(k+1) > 1, sequence gives A000961(k).

8, 25, 121, 2187, 32761

Offset

1,1

Comments

Equivalently, prime powers (either A000961 or A246655) q such that q and the next prime power are both composite numbers. - Paolo Xausa, Oct 25 2023

Links

Table of n, a(n) for n=1..5.

Mathematica

With[{upto=33000}, Map[First, Select[Partition[Select[Range[upto], PrimePowerQ], 2, 1], NoneTrue[#, PrimeQ]&]]] (* Paolo Xausa, Oct 25 2023 *)

Crossrefs

Bisection of A068435.

Cf. A000961, A025474, A246655, A366835.

Sequence in context: A139026 A135942 A181207 * A069586 A253237 A275151

Adjacent sequences: A068312 A068313 A068314 * A068316 A068317 A068318

Keyword

nonn,hard,more

Author

Naohiro Nomoto, Mar 08 2002

Extensions

Definition corrected by Jinyuan Wang, Sep 05 2020

Status

approved