A225039 a(1)=2, a(2)=3, for n>=3, a(n) is the n-th number which is obtained by application Eratosthenes-like sieve to sequence: odd part of digit sum of 5^m, m>=1.

2, 3, 5, 7, 13, 11, 19, 23, 17, 29, 59, 61, 31, 67, 37, 41, 79, 89, 83, 53, 103, 109, 137, 149, 151, 127, 167, 43, 211, 191, 199, 97, 181, 197, 193, 241, 269, 113, 233, 257, 139, 311, 317, 293, 283, 263, 349, 409, 173, 47, 353, 419, 431, 389, 401, 439, 463, 461

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 5^m with 13^m, then we obtain a sequence containing 25. - Vladimir Shevelev, Dec 17 2014

Links

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

Crossrefs

Cf. A000040, A221858, A225017, A225040, A225093, A251964, A252280, A252281, A252282, A252283.

Programs

Mathematica

Flatten[{{2,3,5}, DeleteDuplicates[Select[Map[#/(2^IntegerExponent[#,2] 5^IntegerExponent[#,5])&[Total[IntegerDigits[5^#]]]&, Range[2,199]], PrimeQ]]}] (* Peter J. C. Moses, Apr 25 2013 *)

Extensions

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