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A036345
Divisible by its 'even' sum of prime factors (counted with multiplicity).
2
2, 4, 16, 30, 60, 70, 72, 84, 220, 240, 256, 286, 288, 308, 378, 440, 450, 476, 528, 540, 560, 576, 594, 624, 646, 648, 728, 800, 884, 900, 960, 1040, 1056, 1080, 1160, 1170, 1248, 1276, 1404, 1456, 1496, 1530, 1748, 1776, 1798, 1824, 1976, 2322, 2408, 2464
OFFSET
1,1
LINKS
David A. Corneth, Table of n, a(n) for n = 1..10000 (terms a(n) for n = 2..1002 from Harvey P. Dale).
EXAMPLE
646 = 2*17*19 so the sum of prime factors (with multiplicity) is 2+17+19 = 38 which is even and a divisor of 646 so 646 is in the sequence.
MATHEMATICA
dspfQ[n_]:=Module[{spf=Total[Times@@@FactorInteger[n]]}, EvenQ[spf] && Divisible[n, spf]]; Select[Range[4, 2500, 2], dspfQ] (* Harvey P. Dale, Oct 06 2011 *)
PROG
(PARI) is(n) = my(f = factor(n), s = sum(i = 1, #f~, f[i, 1] * f[i, 2])); s > 0 && s % 2 == 0 && n % s == 0 \\ David A. Corneth, Feb 07 2019
CROSSREFS
Sequence in context: A144797 A173746 A095803 * A032464 A171381 A334083
KEYWORD
nonn
AUTHOR
Patrick De Geest, Dec 15 1998
EXTENSIONS
Offset corrected and a(1) = 2 added by Thomas Ordowski, Feb 07 2019
STATUS
approved