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 A068315 #23 Dec 25 2024 21:02:10
%S A068315 8,25,121,2187,32761
%N A068315 For numbers k such that A025474(k) > 1 and A025474(k+1) > 1, sequence gives A000961(k).
%C A068315 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
%F A068315 a(n) = A246655(A379156(n)). - _Gus Wiseman_, Dec 24 2024
%e A068315 The interval (121,122,123,124,125) contains no primes, so 121 is in the sequence. - _Gus Wiseman_, Dec 24 2024
%t A068315 With[{upto=33000},Map[First,Select[Partition[Select[Range[upto],PrimePowerQ],2,1],NoneTrue[#,PrimeQ]&]]] (* _Paolo Xausa_, Oct 25 2023 *)
%Y A068315 Bisection of A068435.
%Y A068315 For perfect powers instead of prime powers we have A116086, indices A274605.
%Y A068315 The position of a(k) in the prime powers A246655 is A379156(k).
%Y A068315 For just one prime we have A379157, indices A379155.
%Y A068315 A000015 gives the least prime power >= n.
%Y A068315 A000040 lists the primes, differences A001223.
%Y A068315 A031218 gives the greatest prime power <= n.
%Y A068315 A046933 gives run-lengths of composites between primes.
%Y A068315 A065514 gives the greatest prime power < prime(n), difference A377289.
%Y A068315 A246655 lists the prime powers, differences A057820.
%Y A068315 A366833 counts prime powers between primes, see A053607, A304521.
%Y A068315 A366835 counts primes between prime powers.
%Y A068315 Cf. A025474, A067871, A080101, A080769, A175106, A345531, A377281, A377287, A378368.
%K A068315 nonn,hard,more
%O A068315 1,1
%A A068315 _Naohiro Nomoto_, Mar 08 2002
%E A068315 Definition corrected by _Jinyuan Wang_, Sep 05 2020