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 A305900 Filter sequence for a(primes > 3) = constant sequences. 15
 1, 2, 3, 4, 5, 6, 5, 7, 8, 9, 5, 10, 5, 11, 12, 13, 5, 14, 5, 15, 16, 17, 5, 18, 19, 20, 21, 22, 5, 23, 5, 24, 25, 26, 27, 28, 5, 29, 30, 31, 5, 32, 5, 33, 34, 35, 5, 36, 37, 38, 39, 40, 5, 41, 42, 43, 44, 45, 5, 46, 5, 47, 48, 49, 50, 51, 5, 52, 53, 54, 5, 55, 5, 56, 57, 58, 59, 60, 5, 61, 62, 63, 5, 64, 65, 66, 67, 68, 5, 69, 70, 71, 72, 73, 74, 75, 5, 76 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For all i, j:   a(i) = a(j) => A305801(i) = A305801(j) => A305800(i) = A305800(j).   a(i) = a(j) => A007949(i) = A007949(j).   a(i) = a(j) => A305893(i) = A305893(j). LINKS Antti Karttunen, Table of n, a(n) for n = 1..100000 FORMULA For n <= 5, a(n) = n, for >= 5, a(n) = 5 when n is a prime, and a(n) = 3+n-A000720(n) when n is a composite. PROG (PARI) A305900(n) = if(n<=5, n, if(isprime(n), 5, 3+n-primepi(n))); CROSSREFS Cf. A305800, A305801, A305893. Cf. also A305901, A305902, A305903 (this filter applied to various permutations of N). Sequence in context: A099033 A187786 A002330 * A287943 A305211 A091951 Adjacent sequences:  A305897 A305898 A305899 * A305901 A305902 A305903 KEYWORD nonn AUTHOR Antti Karttunen, Jun 14 2018 STATUS approved

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)