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A170819 a(n) = product of distinct primes of form 4k-1 that divide n. 4
1, 1, 3, 1, 1, 3, 7, 1, 3, 1, 11, 3, 1, 7, 3, 1, 1, 3, 19, 1, 21, 11, 23, 3, 1, 1, 3, 7, 1, 3, 31, 1, 33, 1, 7, 3, 1, 19, 3, 1, 1, 21, 43, 11, 3, 23, 47, 3, 7, 1, 3, 1, 1, 3, 11, 7, 57, 1, 59, 3, 1, 31, 21, 1, 1, 33, 67, 1, 69, 7, 71, 3, 1, 1, 3, 19, 77, 3, 79, 1, 3, 1, 83, 21, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Multiplicative with a(p^e) = p*A011765(p+1), e>0. - R. J. Mathar, Jun 07 2011

LINKS

Table of n, a(n) for n=1..85.

MAPLE

A170819 := proc(n) a := 1 ; for p in numtheory[factorset](n) do if p mod 4 = 3 then a := a*p ; end if; end do: a ; end proc:

seq(A170819(n), n=1..20) ; # R. J. Mathar, Jun 07 2011

PROG

(PARI) for(n=1, 99, t=select(x->x%4==3, factor(n)[, 1]); print1(prod(i=1, #t, t[i])", "))

CROSSREFS

Cf. A170817-A170818, A097706, A083025, A007947.

Sequence in context: A058735 A107294 A161788 * A140211 A248101 A097706

Adjacent sequences:  A170816 A170817 A170818 * A170820 A170821 A170822

KEYWORD

nonn,mult

AUTHOR

N. J. A. Sloane, Dec 23 2009

EXTENSIONS

Extended with PARI program by M. F. Hasler, Dec 23 2009

STATUS

approved

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Last modified November 17 19:53 EST 2017. Contains 294834 sequences.