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A013632 a(n) = nextprime(n)-n. 26
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 29 17:00 EDT 2017. Contains 287253 sequences.