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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. Subset of A192272. - Paolo P. Lava, Jan 05 2012 LINKS Table of n, a(n) for n=1..26. Jon Perry, Anti-perfects, anti-amicables and other records. EXAMPLE n=5186, the anti-divisor sum: 3+4+11+23+41+253+451+943+3457 = 5186. MAPLE A073930:= proc(q) local a, k, n; for n from 1 to q do a:=0; for k from 2 to n-1 do if abs((n mod k)-k/2)<1 then a:=a+k; fi; od; if a=n then print(n); fi; od; end: A073930(10^10); # Paolo P. Lava, Mar 11 2013 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

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Last modified June 2 22:56 EDT 2023. Contains 363102 sequences. (Running on oeis4.)