OFFSET
1,2
COMMENTS
EXAMPLE
Anti-divisors of 77 are 2, 3, 5, 9, 14, 17, 22, 31, 51. Their sum is 154 and 154/77=2.
MAPLE
MATHEMATICA
a066417[n_Integer] := Total[Cases[Range[2, n - 1], _?(Abs[Mod[n, #] - #/2] < 1 &)]]; a214842[n_Integer] := Select[Range[n], IntegerQ[a066417[#]/#] &];
a214842[1200] (* Michael De Vlieger, Aug 08 2014 *)
PROG
(Python)
A214842 = [n for n in range(1, 10**4) if not (sum([d for d in range(2, n, 2) if n%d and not 2*n%d])+sum([d for d in range(3, n, 2) if n%d and 2*n%d in [d-1, 1]])) % n]
# Chai Wah Wu, Aug 12 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) = denominator(sad(n)/n) == 1; \\ Michel Marcus, Oct 12 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Paolo P. Lava, Mar 08 2013
EXTENSIONS
Verified there are no missing terms up to a(24) by Donovan Johnson, Apr 13 2013
a(25)-a(27) by Jud McCranie, Aug 31 2019
a(28)-a(32) by Jud McCranie, Oct 10 2019
STATUS
approved