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A133230 Largest index-sum i+j such that prime(i)+prime(j)=4*n^2. a(0)=-1 to indicate that there is no such pair of primes. 2
-1, 2, 8, 15, 22, 31, 41, 53, 63, 77, 90, 105, 123, 138, 157, 175, 194, 215, 237, 259, 281, 306, 330, 355, 382, 410, 437, 468, 498, 527, 558, 588, 623, 656, 689, 727, 762, 797, 836, 872, 911, 952, 992, 1033, 1076, 1119, 1161, 1205, 1249, 1294, 1341, 1390, 1434, 1483, 1534, 1585, 1634, 1687, 1738, 1791, 1842, 1898 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..61.

FORMULA

a(n)= max(i+j), 1<=i<=j: A000040(i)+A000040(j)=A016742(n). - R. J. Mathar, Apr 22 2008

MAPLE

A133230 := proc(n) local a016742, i, j, a ; a016742 := 4*n^2 ; a := -1 ; if n =0 then RETURN(-1) ; fi ; for i from 1 to numtheory[pi](a016742-1) do if isprime(a016742-ithprime(i)) then j := numtheory[pi](a016742-ithprime(i)) : a := max(a, i+j) ; fi ; od: RETURN(a) ; end: seq(A133230(n), n=0..80) ; # R. J. Mathar, Apr 22 2008

CROSSREFS

Cf. A000040, A005843, A016742, A113631, A133229.

Sequence in context: A213082 A246304 A063286 * A318242 A318272 A244476

Adjacent sequences:  A133227 A133228 A133229 * A133231 A133232 A133233

KEYWORD

sign

AUTHOR

Alexander R. Povolotsky, Dec 19 2007

EXTENSIONS

Edited and extended by R. J. Mathar, Apr 22 2008

STATUS

approved

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Last modified May 9 23:39 EDT 2021. Contains 343746 sequences. (Running on oeis4.)