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A305900
Filter sequence for a(primes > 3) = constant sequences.
26
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
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
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. also A305901, A305902, A305903 (this filter applied to various permutations of N).
Sequence in context: A373594 A374040 A374478 * A287943 A305211 A091951
KEYWORD
nonn
AUTHOR
Antti Karttunen, Jun 14 2018
STATUS
approved