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A002374 Largest prime <= n in any decomposition of 2n into a sum of two odd primes.
(Formerly M2278 N0900)
11
3, 3, 5, 5, 7, 5, 7, 7, 11, 11, 13, 11, 13, 13, 17, 17, 19, 17, 19, 13, 23, 19, 19, 23, 23, 19, 29, 29, 31, 23, 29, 31, 29, 31, 37, 29, 37, 37, 41, 41, 43, 41, 43, 31, 47, 43, 37, 47, 43, 43, 53, 47, 43, 53, 53, 43, 59, 59, 61, 53, 59, 61, 59, 61, 67, 53, 67, 67, 71, 71, 73, 59 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

REFERENCES

D. H. Lehmer, Guide to Tables in the Theory of Numbers. Bulletin No. 105, National Research Council, Washington, DC, 1941, p. 80.

N. Pipping, Neue Tafeln fuer das Goldbarsche Gesetz nebst Berichtungen zu den Haussnerschen Tafeln, Finska Vetenskaps-Societeten, Comment. Physico Math.. 4 (No. 4, 1927), 27 pp.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

T. D. Noe, Table of n, a(n) for n = 3..10000

FORMULA

a(n) = n - A047160(n) = A112823(n) (for n >= 3). - Jason Kimberley, Aug 31 2011

MATHEMATICA

nmax = 74; a[n_] := (k = 0; While[k < n && (!PrimeQ[n-k] || !PrimeQ[n+k]), k++]; If[k == n, n+1, n-k]); Table[a[n], {n, 3, nmax}](* Jean-Fran├žois Alcover, Nov 14 2011, after Jason Kimberley *)

PROG

(PARI) a(n)=forstep(k=n, 1, -1, if(isprime(k) && isprime(2*n-k), return(k))) \\ Charles R Greathouse IV, Feb 07 2017

CROSSREFS

Cf. A002372, A002373, A014092.

Essentially the same as A112823. - Franklin T. Adams-Watters, Jan 25 2010

Sequence in context: A266251 A021302 A004649 * A261046 A226482 A110560

Adjacent sequences:  A002371 A002372 A002373 * A002375 A002376 A002377

KEYWORD

nonn,nice,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Larry Reeves (larryr(AT)acm.org), Sep 21 2000

STATUS

approved

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Last modified June 25 20:26 EDT 2017. Contains 288730 sequences.