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A046920 Number of ways to express n as p+2a^2; p = 1 or prime, a >= 0. 5
1, 1, 2, 1, 2, 0, 2, 0, 2, 1, 2, 0, 3, 0, 2, 0, 1, 0, 4, 1, 3, 0, 2, 0, 3, 0, 1, 0, 2, 0, 4, 0, 2, 1, 2, 0, 4, 0, 3, 0, 2, 0, 3, 0, 3, 0, 2, 0, 4, 0, 3, 1, 2, 0, 5, 0, 1, 0, 2, 0, 6, 0, 3, 0, 1, 0, 3, 0, 4, 0, 2, 0, 5, 1, 4, 0, 2, 0, 6, 0, 3, 0, 2, 0, 4, 0, 2, 0, 3, 0, 6, 0, 2, 0, 1, 0, 4, 0, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

L. Hodges, A lesser-known Goldbach conjecture, Math. Mag., 66 (1993), 45-47.

Index entries for sequences related to Goldbach conjecture

PROG

(Haskell)

a046920 n = length $ filter ((\x -> x == 1 || a010051 x == 1) . (n -)) $

                            takeWhile (< n) a001105_list

-- Reinhard Zumkeller, Apr 03 2013

CROSSREFS

Cf. A042978, A046921, A046922, A046923, A060003, A143539.

Cf. A016067, A008578, A010051, A001105.

Sequence in context: A117167 A117169 A274263 * A107599 A156836 A287438

Adjacent sequences:  A046917 A046918 A046919 * A046921 A046922 A046923

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified October 23 21:57 EDT 2019. Contains 328373 sequences. (Running on oeis4.)