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 A070776 Numbers k such that number of terms in the k-th cyclotomic polynomial is equal to the largest prime factor of k. 20
 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 34, 36, 37, 38, 40, 41, 43, 44, 46, 47, 48, 49, 50, 52, 53, 54, 56, 58, 59, 61, 62, 64, 67, 68, 71, 72, 73, 74, 76, 79, 80, 81, 82, 83, 86, 88, 89, 92, 94, 96, 97, 98, 100 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k such that A051664(k) = A006530(k). This is also numbers in the form of 2^i*p^j, i >= 0 and j >= 0, p is an odd prime number. - Lei Zhou, Feb 18 2012 From Zhou's formulation (where the exponents i and j should actually have been specified as i > 0 OR j > 0, to exclude 1) it follows that this is a subsequence of A324109. It also follows that A005940(a(n)) = A324106(a(n)) for all n >= 1. - Antti Karttunen, Feb 15 2019 Also from Zhou's formulation, the union (disjoint) of A000079\{1} and A336101. - Peter Munn, Jul 16 2020 Numbers k>=2 such that A078701(k) = A299766(k). - Juri-Stepan Gerasimov, Jun 02 2021 LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 EXAMPLE n=10: Cyclotomic[10,x]=1-x+x^2-x^3+x^4 with 5 terms [including 1] which equals largest prime factor (5) of 10=n. MATHEMATICA Select[Range, (a=FactorInteger[#]; b=Length[a]; (b==1)||((b==2)&&(a[][]==2)))&] (* Lei Zhou, Feb 18 2012 *) PROG (PARI) A006530(n) = if(n>1, vecmax(factor(n)[, 1]), 1); \\ From A006530. A051664(n) = length(select(x->x!=0, Vec(polcyclo(n)))); \\ After program in A051664 A070536(n) = (A051664(n) - A006530(n)); isA070776(n) = (!A070536(n)); \\ Antti Karttunen, Feb 15 2019 k=0; n=0; while(k<10000, n++; if(isA070776(n), k++; write("b070776.txt", k, " ", n))); CROSSREFS Positions of zeros in A070536. Cf. A005940, A006530, A051664, A061345, A070537 (complement), A324106, A324111. Subsequence of A324109. Subsequences: A000079\{1}, A336101. Sequence in context: A075592 A285801 A324109 * A320230 A076564 A325044 Adjacent sequences:  A070773 A070774 A070775 * A070777 A070778 A070779 KEYWORD nonn,easy AUTHOR Labos Elemer, May 07 2002 STATUS approved

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Last modified May 24 19:38 EDT 2022. Contains 354043 sequences. (Running on oeis4.)