

A013632


a(n) = nextprime(n)n.


29



2, 1, 1, 2, 1, 2, 1, 4, 3, 2, 1, 2, 1, 4, 3, 2, 1, 2, 1, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1, 2, 1, 6, 5, 4, 3, 2, 1, 4, 3, 2, 1, 2, 1, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1, 2, 1, 6, 5, 4, 3, 2, 1, 4, 3, 2, 1, 2, 1, 6, 5, 4, 3, 2, 1, 4, 3, 2, 1, 6, 5, 4, 3, 2, 1, 8, 7, 6, 5, 4, 3, 2, 1, 4, 3, 2, 1, 2, 1, 4, 3
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OFFSET

0,1


COMMENTS

Alternatively, a(n) = smallest k such that n+k is prime.  N. J. A. Sloane, Nov 18 2015
Except for a(0) and a(1), a(n) is the least k such that the GCD( n!, n+k) = 1.  Robert G. Wilson v, Nov 05 2010
This sequence uses the "strictly larger" variant A151800 of the nextprime function, rather than A007918. Therefore all terms are positive and a(n)=1 iff n+1 is a prime.  M. F. Hasler, Sep 09 2015


LINKS

Table of n, a(n) for n=0..104.
Brăduţ Apostol, Laurenţiu Panaitopol, Lucian Petrescu, László Tóth, Some properties of a sequence defined with the aid of prime numbers, arXiv:1503.01086 [math.NT], 2015.


MAPLE

[ seq(nextprime(i)i, i=0..100) ];


MATHEMATICA

f[n_] := NextPrime@n  n; Array[f, 105, 0] (* Robert G. Wilson v, Nov 05 2010 *)


PROG

(PARI) a(n) = nextprime(n+1)  n; \\ Michel Marcus, Mar 04 2015


CROSSREFS

Cf. A007918, A151800.
Sequence in context: A049843 A131374 A207409 * A080121 A122901 A001917
Adjacent sequences: A013629 A013630 A013631 * A013633 A013634 A013635


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Incorrect comment removed by Charles R Greathouse IV, Mar 18 2010
More terms from Robert G. Wilson v, Nov 05 2010


STATUS

approved



