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A244408 Even numbers 2n such that the smallest prime p satisfying p+q=2n (q prime) is greater than or equal to sqrt(2n). 5
4, 6, 8, 12, 18, 24, 30, 38, 98, 122, 126, 128, 220, 302, 308, 332, 346, 488, 556, 854, 908, 962, 992, 1144, 1150, 1274, 1354, 1360, 1362, 1382, 1408, 1424, 1532, 1768, 1856, 1928, 2078, 2188, 2200, 2438, 2512, 2530, 2618, 2642, 3458, 3818, 3848 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(74) = 63274 is probably the last term. Oliveira e Silva's work shows there are no more terms below 4*10^18. The largest p below that is p = 9781 for 2n = 3325581707333960528, where sqrt(2n) = 1823617752. - Jens Kruse Andersen, Jul 03 2014

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..74

Tomás Oliveira e Silva, Goldbach conjecture verification

Index entries for sequences related to Goldbach conjecture

EXAMPLE

The smallest prime for 38 is 7, and 7 >= sqrt(38).

PROG

(PARI) for(n=1, 50000, forprime(p=2, n, if(isprime(2*n-p), if(p>=sqrt(2*n), print1(2*n", ")); break))) \\ Jens Kruse Andersen, Jul 03 2014

(Haskell)

a244408 n = a244408_list !! (n-1)

a244408_list = map (* 2) $ filter f [2..] where

   f x = sqrt (fromIntegral $ 2 * x) <= fromIntegral (a020481 x)

-- Reinhard Zumkeller, Jul 07 2014

CROSSREFS

Cf. A020481, A002373, A025018, A025019.

Sequence in context: A161785 A234523 A178549 * A023374 A053016 A078785

Adjacent sequences:  A244405 A244406 A244407 * A244409 A244410 A244411

KEYWORD

nonn

AUTHOR

Jon Perry, Jun 27 2014

STATUS

approved

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Last modified February 25 11:08 EST 2018. Contains 299653 sequences. (Running on oeis4.)