

A225063


Smallest k such that (k1)*prime(n) +/ k are both prime.


1



5, 4, 2, 3, 4, 3, 3, 4, 15, 6, 4, 6, 6, 3, 6, 3, 4, 7, 3, 7, 18, 4, 6, 4, 3, 7, 6, 25, 7, 3, 3, 4, 3, 31, 6, 4, 3, 6, 3, 13, 10, 12, 4, 3, 13, 4, 6, 3, 21, 4, 43, 10, 4, 9, 6, 10, 7, 21, 28, 19, 3, 6, 13, 4, 6, 33, 7, 15, 28, 19, 10, 6, 18, 18, 6, 21, 4, 36
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OFFSET

1,1


LINKS

Table of n, a(n) for n=1..78.


EXAMPLE

a(1) = 5 because (51)*2  5 = 3 and (51)*2 + 5 = 13 are both prime;
a(2) = 4 because (41)*3  4 = 5 and (41)*3 + 4 = 13 are both prime;
a(3) = 2 because (21)*5  2 = 3 and (21)*5 + 2 = 7 are both prime;
a(4) = 3 because (31)*7  3 = 11 and (31)*7 + 3 = 17 are both prime;
a(5) = 4 because (41)*11  4 = 29 and (41)*11 + 4 = 37 are both prime;
a(6) = 3 because (31)*13  3 = 23 and (31)*13 + 3 = 29 are botn prime;
a(7) = 3 because (31)*17  3 = 31 and (31)*17 + 3 = 37 are both prime;
a(8) = 4 because (41)*19  4 = 53 and (41)*19 + 4 = 61 are both prime;
a(9) = 15 because (151)*23  15 = 307 and (151)*23 + 15 = 337 are both prime.


MATHEMATICA

sk[n_]:=Module[{k=2}, While[!PrimeQ[(k1)n+k]!PrimeQ[(k1)nk], k++]; k]; sk/@Prime[Range[80]] (* Harvey P. Dale, Oct 04 2015 *)


CROSSREFS

Sequence in context: A246966 A081749 A074825 * A309442 A213205 A094778
Adjacent sequences: A225060 A225061 A225062 * A225064 A225065 A225066


KEYWORD

nonn,less


AUTHOR

JuriStepan Gerasimov, Apr 26 2013


EXTENSIONS

Corrected by R. J. Mathar, May 04 2013


STATUS

approved



