1,1

Numbers whose prime factorization k = 2^i_1 * 3^i_2 * 5^i_3 * .. * 17^i_7 * 19^i_8 satisfies 2*i_1 + 3*i_2 + ... + 17*i_7 + 19*i_8 = 20. - N. J. A. Sloane, Jan 16 2019

Table of n, a(n) for n=1..26.

E.g. 51 = 3 * 17 and 3 + 17 = 20. 1024 = 2^10 and 10*2 = 20.

pfs20Q[n_]:=Total[#[[1]]#[[2]]&/@FactorInteger[n]]==20; Select[Range[ 10000], pfs20Q] (* Harvey P. Dale, Jan 17 2019 *)

Numbers k such that A001414(k) = 20.

Sequence in context: A039474 A253020 A020180 * A075894 A229274 A044140

Adjacent sequences: A049325 A049326 A049327 * A049329 A049330 A049331

fini,full,nonn

Rawlyn Watson (rawlyn(AT)chplayers.freeserve.co.uk)

Corrected by Frank Ellermann, Jun 07 2001

Further corrected by N. J. A. Sloane, Jan 16 2019 at the suggestion of Harvey P. Dale.

approved