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Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!) A353497 The smallest prime factor of n, reduced modulo 4, with a(1) = 1. 2 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 1, 2, 1, 2, 3, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 3, 2, 1, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 1, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3 (list; graph; refs; listen; history; text; internal format) OFFSET 1,2 LINKS Antti Karttunen, Table of n, a(n) for n = 1..65537 FORMULA a(n) = A010873(A020639(n)). For all n >= 1, A010873(n) = A010873(A353490(n)*a(n)). For all n >= 1, a(2n-1) = A010873(A353490(2n-1)*(2n-1)). For all n >= 1, a(A276086(n)) = A353526(n). MATHEMATICA a[n_] := Mod[FactorInteger[n][[1, 1]], 4]; Array[a, 100] (* Amiram Eldar, Apr 26 2022 *) PROG (PARI) A020639(n) = if(1==n, n, vecmin(factor(n)[, 1])); A353497(n) = (A020639(n)%4); (Python) from sympy import factorint def a(n): return 1 if n==1 else (2 if n%2==0 else min(factorint(n))%4) print([a(n) for n in range(1, 106)]) # Michael S. Branicky, Apr 26 2022 CROSSREFS Cf. A010873, A020639, A353490, A353526. Cf. also A353493. Sequence in context: A032452 A084199 A277745 * A320858 A304111 A030314 Adjacent sequences: A353494 A353495 A353496 * A353498 A353499 A353500 KEYWORD nonn AUTHOR Antti Karttunen, Apr 26 2022 STATUS approved

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Last modified August 18 13:06 EDT 2024. Contains 375269 sequences. (Running on oeis4.)