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A072202 Same numbers of prime factors of forms 4*k+1 and 4*k+3, counted with multiplicity. 12
1, 2, 4, 8, 15, 16, 30, 32, 35, 39, 51, 55, 60, 64, 70, 78, 87, 91, 95, 102, 110, 111, 115, 119, 120, 123, 128, 140, 143, 155, 156, 159, 174, 182, 183, 187, 190, 203, 204, 215, 219, 220, 222, 225, 230, 235, 238, 240, 246, 247, 256, 259, 267, 280, 286, 287, 291 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Equivalently, numbers n such that A083025(n) = A065339(n), indices of zeros in A079635.
Closed under multiplication.
Closed with respect to permutation A267099. - Antti Karttunen, Feb 03 2016
LINKS
EXAMPLE
825 = 3*5*5*11 = [(4*0+3)*(4*2+3)]*[(4*1+1)*(4*1+1)], therefore 825 is a term.
MATHEMATICA
f[n_]:=Plus@@Last/@Select[If[==1, {}, FactorInteger[n]], Mod[#[[1]], 4]==1&]; Table[f[n], {n, 100}] (* Ray Chandler, Dec 18 2011 *)
PROG
(Haskell)
a072202 n = a072202_list !! (n-1)
a072202_list = [x | x <- [1..], a083025 x == a065339 x]
-- Reinhard Zumkeller, Jan 10 2012
(Scheme) (define A072202 (ZERO-POS 1 1 A079635)) ;; [requires also my IntSeq-library] - Antti Karttunen, Feb 03 2016
(PARI) isok(n) = {my(f = factor(n)); sum(k=1, #f~, ((f[k, 1] % 4)==1)*f[k, 2]) == sum(k=1, #f~, ((f[k, 1] % 4)==3)*f[k, 2]); } \\ Michel Marcus, Feb 05 2016
CROSSREFS
Primitive elements are {2} U A080774. - Franklin T. Adams-Watters, Dec 16 2011.
Subsequence of A078613 and of A268381.
Sequence in context: A084561 A277166 A078613 * A354189 A275474 A354192
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jul 03 2002
STATUS
approved

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Last modified February 26 13:41 EST 2024. Contains 370352 sequences. (Running on oeis4.)