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A046920
Number of ways to express n as p+2a^2; p = 1 or prime, a >= 0.
6
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
OFFSET
1,3
PROG
(Haskell)
a046920 n = length $ filter ((\x -> x == 1 || a010051 x == 1) . (n -)) $
takeWhile (< n) a001105_list
-- Reinhard Zumkeller, Apr 03 2013
KEYWORD
nonn
STATUS
approved