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 A188172 Number of divisors d of n of the form d == 7 (mod 8). 7
 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 2, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,63 COMMENTS a(A188226(n))=n and a(m)<>n for m=0; a(A141164(n))=1. - Reinhard Zumkeller, Mar 26 2011 LINKS _Reinhard Zumkeller_, Table of n, a(n) for n = 1..10000 M. D. Hirschhorn, The number of representations of a number by various forms, Discrete Mathematics 298 (2005), 205-211. FORMULA A188170(n)+a(n) = A001842(n). A188169(n)+A188170(n)-A188171(n)-a(n) = A002325(n). EXAMPLE a(A007522(i)) = 1, any i. MAPLE sigmamr := proc(n, m, r) local a, d ; a := 0 ; for d in numtheory[divisors](n) do if modp(d, m) = r then a := a+1 ; end if; end do: a; end proc: A188172 := proc(n) sigmamr(n, 8, 7) ; end proc: PROG (Haskell) a188172 n = length \$ filter ((== 0) . mod n) [7, 15..n] -- Reinhard Zumkeller, Mar 26 2011 CROSSREFS Cf. A004771. Sequence in context: A083895 A093488 A085858 * A106671 A033776 A117371 Adjacent sequences:  A188169 A188170 A188171 * A188173 A188174 A188175 KEYWORD nonn,easy AUTHOR R. J. Mathar, Mar 23 2011 STATUS approved

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