A115206 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A115206

Least number d such that prime(n) -/+ 2d form a prime pair; prime(n) being the n-th prime.

1, 2, 3, 3, 3, 6, 3, 6, 6, 3, 6, 12, 3, 3, 6, 9, 3, 6, 3, 9, 12, 9, 15, 6, 3, 3, 15, 12, 12, 9, 15, 6, 9, 6, 3, 18, 15, 3, 6, 9, 21, 15, 15, 21, 6, 30, 15, 24, 3, 6, 15, 6, 3, 3, 6, 21, 3, 6, 27, 12, 12, 21, 18, 18, 9, 15, 18, 9, 3, 21, 15, 3, 15, 18, 15, 12, 9, 6, 15, 6, 6, 12, 9, 12, 9, 42, 9

(list; graph; refs; listen; history; text; internal format)

OFFSET

3,2

LINKS

Table of n, a(n) for n=3..89.

FORMULA

a(n) = A078611(n)/2.

MATHEMATICA

f[n_] := Block[{k = 1, p = Prime@n}, While[ !PrimeQ[p - 2k] || !PrimeQ[p + 2k], k++ ]; k]; Table[f[n], {n, 3, 90}] (* Robert G. Wilson v, Mar 14 2006 *)

CROSSREFS

Cf. A078611.

Sequence in context: A133700 A087688 A126854 * A093653 A205442 A049982

Adjacent sequences: A115203 A115204 A115205 * A115207 A115208 A115209

KEYWORD

nonn

AUTHOR

Lekraj Beedassy, Mar 04 2006

EXTENSIONS

Corrected by N. J. A. Sloane, Mar 05 2006

More terms from Robert G. Wilson v, Mar 14 2006

STATUS

approved