

A103153


a(n) = smallest odd prime p such that 2*n+1 = 2*p + A000040(k) for some k>1, or 0 if no such prime exists.


8



0, 0, 0, 3, 3, 3, 5, 3, 3, 5, 3, 3, 5, 3, 7, 5, 3, 3, 5, 5, 3, 7, 3, 3, 5, 3, 7, 5, 3, 7, 5, 3, 3, 5, 5, 3, 7, 3, 3, 5, 5, 3, 7, 3, 19, 5, 3, 7, 5, 11, 3, 11, 3, 3, 5, 3, 3, 5, 3, 7, 5, 11, 7, 11, 11, 3, 11, 3, 13, 5, 3, 3, 5, 5, 7, 7, 3, 3, 5, 5, 3, 7, 5, 3, 7, 3, 13, 5, 3, 7, 5, 3, 3, 5, 5, 7, 7, 3
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OFFSET

1,4


LINKS

Table of n, a(n) for n=1..98.


EXAMPLE

For n < 4 there are no such primes, thus a(1)a(3)=0. For n=4, 2*4+1 = 9 = 2*3+3, thus a(4)=3. For n=7, 2*7+1 = 15 = 2*5+5, thus a(7)=7.


MATHEMATICA

Do[m = 3; While[ ! (PrimeQ[m] && ((n  2*m) > 2) && PrimeQ[n  2*m]), m = m + 2]; Print[m], {n, 9, 299, 2}]


PROG

(Scheme:) (define (A103153 n) (let ((ind (A103507 n))) (if (zero? ind) 0 (A000040 ind))))


CROSSREFS

a(n)=0 if A103507(n)=0, otherwise A000040(A103507(n)). Cf. A103151, A103152, A002373.
Cf. A195352 (similar definition, but p=2 is allowed).
Sequence in context: A049613 A002373 A236569 * A162022 A318240 A262289
Adjacent sequences: A103150 A103151 A103152 * A103154 A103155 A103156


KEYWORD

nonn


AUTHOR

Lei Zhou, Feb 09 2005


EXTENSIONS

Edited and Scheme code added by Antti Karttunen, Jun 19 2007
Definition corrected by Hugo Pfoertner, Sep 16 2011


STATUS

approved



