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A073930 Numbers that are equal to the sum of their anti-divisors. 11
5, 8, 41, 56, 946, 5186, 6874, 8104, 17386, 27024, 84026, 167786, 2667584, 4921776, 27914146, 505235234, 3238952914, 73600829714, 455879783074, 528080296234, 673223621664, 4054397778846, 4437083907194, 4869434608274, 6904301600914, 7738291969456 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
See A066272 for definition of anti-divisor.
LINKS
EXAMPLE
n=5186, the anti-divisor sum: 3+4+11+23+41+253+451+943+3457 = 5186.
PROG
(Python)
from sympy import divisors
A073930 = [n for n in range(1, 10**5) if sum([2*d for d in divisors(n) if n > 2*d and n % (2*d)] + [d for d in divisors(2*n-1) if n > d >=2 and n % d] + [d for d in divisors(2*n+1) if n > d >=2 and n % d]) == n] # Chai Wah Wu, Aug 14 2014
(PARI) sad(n) = vecsum(select(t->n%t && t<n, concat(concat(divisors(2*n-1), divisors(2*n+1)), 2*divisors(n)))); \\ A066417
isok(n) = sad(n) == n; \\ Michel Marcus, Oct 12 2019
CROSSREFS
Sequence in context: A298935 A258786 A192272 * A342021 A130223 A126750
KEYWORD
nonn,more
AUTHOR
Jason Earls, Sep 03 2002
EXTENSIONS
Two more terms from Lior Manor Mar 03 2004
a(18) from Donovan Johnson, Jun 19 2010
a(19)-a(21) by Jud McCranie, Aug 31 2019
a(22)-a(26) by Jud McCranie, Oct 10 2019
STATUS
approved

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Last modified March 29 11:45 EDT 2024. Contains 371278 sequences. (Running on oeis4.)