A181516 - OEIS

A181516

Primes in A011371.

3, 7, 11, 19, 23, 31, 41, 47, 53, 67, 71, 73, 79, 89, 97, 101, 109, 113, 127, 131, 137, 149, 173, 181, 191, 193, 197, 229, 239, 263, 271, 277, 281, 293, 311, 337, 349, 353, 359, 367, 383, 389, 397, 401, 421, 431, 439, 449, 461, 463, 467, 479, 487, 491, 499

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Primes p such that 2^p divides some factorial m!, but 2^(p+1) does not divide m!.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

f[n_] := n - DigitCount[n, 2, 1]; s={}; Do[If[PrimeQ[(p = f[n])], AppendTo[s, p]], {n, 1, 510, 2}]; s (* Amiram Eldar, Sep 13 2019 *)

Select[Table[n-DigitCount[n, 2, 1], {n, 0, 600}], PrimeQ]//Union (* Harvey P. Dale, Oct 10 2020 *)

CROSSREFS

Cf. A011371.