A062301 - OEIS

A062301

Number of ways writing n-th prime as a sum of two primes.

0, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1

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OFFSET

1,1

COMMENTS

a(n) = 1 if and only if n is in A006512. - Robert Israel, Apr 04 2018

LINKS

Muniru A Asiru, Table of n, a(n) for n = 1..3000

MAPLE

a:= n-> `if`(isprime(ithprime(n)-2), 1, 0):

seq(a(n), n=1..105); # Alois P. Heinz, Oct 02 2020

MATHEMATICA

Table[Sum[(PrimePi[Prime[n] - i] - PrimePi[Prime[n] - i - 1]) (PrimePi[i] - PrimePi[i - 1]), {i, Floor[Prime[n]/2]}], {n, 100}] (* Wesley Ivan Hurt, Apr 04 2018 *)

PROG

(PARI) a(n) = isprime(prime(n) - 2) \\ David A. Corneth, Apr 04 2018

(GAP) P:=Filtered([1..1000], IsPrime);; a:=List(List(List(P, i -> Partitions(i, 2)), k -> Filtered(k, i -> IsPrime(i[1]) and IsPrime(i[2]))), Length); # Muniru A Asiru, Apr 05 2018

CROSSREFS

Equals A061358(A000040(n)).

Cf. A006512, A014092, A025584.

Sequence in context: A284932 A117814 A257000 * A374769 A181712 A288729

Adjacent sequences: A062298 A062299 A062300 * A062302 A062303 A062304

KEYWORD

nonn

AUTHOR

Labos Elemer, Jul 05 2001

EXTENSIONS

Offset changed to 1 by David A. Corneth, Apr 04 2018

STATUS

approved