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A205617 Number of decompositions of 2n into an unordered sum of two non-Ramanujan primes (A174635). 3
0, 0, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 2, 1, 2, 2, 2, 1, 3, 0, 1, 3, 1, 2, 2, 1, 3, 2, 0, 1, 3, 2, 1, 3, 1, 3, 4, 1, 2, 4, 1, 4, 2, 0, 3, 2, 3, 2, 3, 2, 3, 5, 1, 3, 4, 0, 5, 1, 0, 4, 3, 3, 1, 4, 3, 5, 4, 0, 4, 3, 1, 4, 2, 2, 6, 2, 3, 4, 4, 1, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

There are 15 zeros in the first 10^8 terms. a(n) > 0 for n from 315 to 10^8.

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..10000

J. Sondow, Ramanujan primes and Bertrand's postulate, Amer. Math. Monthly 116 (2009), 630-635.

J. Sondow, J. W. Nicholson, and T. D. Noe, Ramanujan Primes: Bounds, Runs, Twins, and Gaps, J. Integer Seq. 14 (2011) Article 11.6.2

EXAMPLE

a(25) = 3. 2*25 = 50 = 7+43 = 13+37 = 19+31 (7, 13, 19, 31, 37, and 43 are all non-Ramanujan primes (A174635)). 50 is the unordered sum of two non-Ramanujan primes in three ways.

CROSSREFS

Cf. A104272, A174635, A173634, A204814, A205301, A205616, A205618.

Sequence in context: A117358 A294333 A321125 * A204112 A186027 A322482

Adjacent sequences:  A205614 A205615 A205616 * A205618 A205619 A205620

KEYWORD

nonn

AUTHOR

John W. Nicholson and Donovan Johnson, Jan 30 2012

STATUS

approved

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Last modified September 20 16:50 EDT 2021. Contains 347586 sequences. (Running on oeis4.)