OFFSET
1,1
COMMENTS
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
EXAMPLE
E.g. 51 = 3 * 17 and 3 + 17 = 20. 1024 = 2^10 and 10*2 = 20.
MATHEMATICA
pfs20Q[n_]:=Total[#[[1]]#[[2]]&/@FactorInteger[n]]==20; Select[Range[ 10000], pfs20Q] (* Harvey P. Dale, Jan 17 2019 *)
CROSSREFS
KEYWORD
fini,full,nonn
AUTHOR
Rawlyn Watson (rawlyn(AT)chplayers.freeserve.co.uk)
EXTENSIONS
Corrected by Frank Ellermann, Jun 07 2001
Further corrected by N. J. A. Sloane, Jan 16 2019 at the suggestion of Harvey P. Dale.
STATUS
approved