cp's OEIS Frontend

A221858 a(1)=2, a(2)=3, for n>=3, a(n) is the n-th number which is obtained by application of Eratosthenes-like sieve (with removing 1's) to sequence: odd part of digit sum of 2^m, m>=1.

%I A221858 #33 Dec 14 2014 15:10:45
%S A221858 2,3,7,5,11,13,19,29,31,41,37,43,47,61,59,67,71,23,17,73,79,89,109,
%T A221858 103,53,107,113,139,151,127,137,83,167,173,181,191,101,193,223,233,
%U A221858 211,199,229,251,239,281,277,241,131,269,263,283,313,311,349,163,317,337,331,307
%N A221858 a(1)=2, a(2)=3, for n>=3, a(n) is the n-th number which is obtained by application of Eratosthenes-like sieve (with removing 1's) to sequence: odd part of digit sum of 2^m, m>=1.
%C A221858 We conjecture that every term is prime;
%C A221858 moreover, we conjecture that the sequence is a permutation of the sequence of all primes.
%C A221858 For comparison, if in the definition we replace 2^m with 13^m, then we obtain a sequence containing 25. - _Vladimir Shevelev_, Dec 07 2014
%H A221858 Peter J. C. Moses, <a href="/A221858/b221858.txt">Table of n, a(n) for n = 1..10000</a>
%t A221858 Flatten[{{2,3},DeleteDuplicates[Select[Map[#/(2^IntegerExponent[#,2])&[Total[IntegerDigits[2^#]]]&,Range[3,300]],PrimeQ]]}] (* _Peter J. C. Moses_, Apr 25 2013 *)
%Y A221858 Cf. A000040, A225017, A225039, A225040, A225093.
%K A221858 nonn,base
%O A221858 1,1
%A A221858 _Vladimir Shevelev_, Apr 25 2013
%E A221858 More terms from _Peter J. C. Moses_, Apr 25 2013