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%I #41 Apr 11 2016 03:49:39
%S 2,3,4,5,8,9,17,25,49,64,121,169,257,289,729,841,1681,1849,3481,5329,
%T 11881,12769,16129,18769,24649,32041,32761,38809,39601,44521,59049,
%U 63001,65537,69169,76729,85849,96721,124609,134689,143641,167281,175561,187489
%N Prime powers (p^k, p prime, k >= 1) such that k*p^k - 1 is also a power of a prime.
%C Of course 1 = p^0 for any prime p, so 1 is definitely the power of a prime (comment in A000961).
%C Only primes of the form 2^m + 1 (2 and Fermat primes) are terms.
%e 8 is in this sequence because both 8 = 2^3 and 3*2^3 - 1 = 23 is prime power.
%o (PARI) ispp(n) = if ((n==1) || isprime(n), return (1), isprimepower(n));
%o isok(n) = ((k=ispp(n)) && ispp(k*n-1)); \\ _Michel Marcus_, Apr 11 2016
%Y Cf. A000961, A019434 (Fermat primes), A092506 (primes of the form 2^m + 1).
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, Apr 09 2016
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