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A049328 Numbers whose prime factors (taken with multiplicity) sum to 20. 0
51, 91, 130, 154, 156, 220, 264, 297, 392, 441, 525, 560, 625, 630, 672, 750, 756, 800, 900, 960, 1024, 1080, 1152, 1215, 1296, 1458 (list; graph; refs; listen; history; text; internal format)
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
LINKS
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
Numbers k such that A001414(k) = 20.
Sequence in context: A253020 A351026 A020180 * A075894 A229274 A044140
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

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Last modified June 23 07:16 EDT 2024. Contains 373629 sequences. (Running on oeis4.)