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A019507 Droll numbers: sum of even prime divisors equals sum of odd prime divisors. 2
72, 240, 672, 800, 2240, 4224, 5184, 6272, 9984, 14080, 17280, 33280, 39424, 48384, 52224, 57600, 93184, 116736, 161280, 174080, 192000, 247808, 304128, 373248, 389120, 451584, 487424, 537600, 565248, 585728, 640000, 718848 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

EXAMPLE

6272 = 2*2*2*2*2*2*2*7*7 is droll since 2+2+2+2+2+2+2 = 14 = 7+7.

PROG

(PARI) isok(n) = {if (n % 2, return (0)); f = factor(n); return (2*f[1, 2] == sum(i=2, #f~, f[i, 1]*f[i, 2])); } \\ Michel Marcus, Jun 21 2013

CROSSREFS

Sequence in context: A064716 A073412 A250749 * A303081 A158488 A165139

Adjacent sequences:  A019504 A019505 A019506 * A019508 A019509 A019510

KEYWORD

nonn

AUTHOR

Mario Velucchi (mathchess(AT)velucchi.it)

STATUS

approved

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Last modified September 21 19:57 EDT 2020. Contains 337273 sequences. (Running on oeis4.)