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 A293235 a(n) is the sum of proper divisors of n that are square. 3
 0, 1, 1, 1, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 5, 1, 10, 1, 5, 1, 1, 1, 5, 1, 1, 10, 5, 1, 1, 1, 21, 1, 1, 1, 14, 1, 1, 1, 5, 1, 1, 1, 5, 10, 1, 1, 21, 1, 26, 1, 5, 1, 10, 1, 5, 1, 1, 1, 5, 1, 1, 10, 21, 1, 1, 1, 5, 1, 1, 1, 50, 1, 1, 26, 5, 1, 1, 1, 21, 10, 1, 1, 5, 1, 1, 1, 5, 1, 10, 1, 5, 1, 1, 1, 21, 1, 50, 10, 30, 1, 1, 1, 5, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,8 COMMENTS a(n) = 1 if and only if n > 1 is squarefree or the square of a prime. - Robert Israel, Oct 08 2017 LINKS Antti Karttunen, Table of n, a(n) for n = 1..16384 FORMULA a(n) = Sum_{d|n, d mul((p[1]^(p[2]+2-(p[2] mod 2))-1)/(p[1]^2-1), p = ifactors(n)[2]): f:= n -> A035316(n) - `if`(issqr(n), n, 0): map(f, [\$1..100]); # Robert Israel, Oct 08 2017 PROG (PARI) A293235(n) = sumdiv(n, d, (d

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Last modified June 17 19:10 EDT 2019. Contains 324198 sequences. (Running on oeis4.)