

A236675


If n is prime, then a(n) is the least composite number not occurring earlier, else a(n) is the least prime not occurring earlier.


3



2, 4, 6, 3, 8, 5, 9, 7, 11, 13, 10, 17, 12, 19, 23, 29, 14, 31, 15, 37, 41, 43, 16, 47, 53, 59, 61, 67, 18, 71, 20, 73, 79, 83, 89, 97, 21, 101, 103, 107, 22, 109, 24, 113, 127, 131, 25, 137, 139, 149, 151, 157, 26, 163, 167, 173, 179, 181, 27, 191, 28, 193
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OFFSET

1,1


COMMENTS

If "composite" is replaced by "nonprime", one gets A026234, a permutation of the integers.


LINKS

Table of n, a(n) for n=1..62.


FORMULA

a(n) = A002808(A000720(n)) if n is prime, a(n) = A000040(nA000720(n)) else.


PROG

(PARI) A236675=n>if(isprime(n), A002808(primepi(n)), prime(nprimepi(n)))
(PARI) c=p=1; vector(99, n, if(isprime(n), while(isprime(c++), ); c, p=nextprime(p+1)))


CROSSREFS

Cf. A026234, A002808, A018252, A097457, A236675.
Sequence in context: A287662 A278376 A057336 * A210771 A115316 A089088
Adjacent sequences: A236672 A236673 A236674 * A236676 A236677 A236678


KEYWORD

nonn


AUTHOR

M. F. Hasler, Jan 29 2014


STATUS

approved



