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.

2, 3, 7, 5, 11, 13, 19, 29, 31, 41, 37, 43, 47, 61, 59, 67, 71, 23, 17, 73, 79, 89, 109, 103, 53, 107, 113, 139, 151, 127, 137, 83, 167, 173, 181, 191, 101, 193, 223, 233, 211, 199, 229, 251, 239, 281, 277, 241, 131, 269, 263, 283, 313, 311, 349, 163, 317, 337, 331, 307

Offset: 1

Author

Vladimir Shevelev, Apr 25 2013

Keywords

• nonn
• base

Comments

We conjecture that every term is prime;

moreover, we conjecture that the sequence is a permutation of the sequence of all primes.

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

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A225017, A225039, A225040, A225093.

Programs

Mathematica

Flatten[{{2,3},DeleteDuplicates[Select[Map[#/(2^IntegerExponent[#,2])&[Total[IntegerDigits[2^#]]]&,Range[3,300]],PrimeQ]]}] (* Peter J. C. Moses, Apr 25 2013 *)

Extensions

More terms from Peter J. C. Moses, Apr 25 2013