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A005089
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Number of distinct primes = 1 mod 4 dividing n.
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3
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0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 2, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 2, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,65
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FORMULA
| Additive with a(p^e) = 1 if p = 1 (mod 4), 0 otherwise.
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MATHEMATICA
| f[n_]:=Length@Select[If[n==1, {}, FactorInteger[n]], Mod[#[[1]], 4]==1&]; Table[f[n], {n, 102}] (* Ray Chandler, Dec 18 2011 *)
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PROG
| (PARI) for(n=1, 100, print1(sumdiv(n, d, isprime(d)*if((d-1)%4, 0, 1)), ", "))
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CROSSREFS
| Cf. A001221, A005091.
Sequence in context: A165766 A102082 A030199 * A119395 A087476 A035162
Adjacent sequences: A005086 A005087 A005088 * A005090 A005091 A005092
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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