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 A082462 Let chi(k) = 1 if prime(k+1) - prime(k) = 2, = 0 otherwise; sequence gives a(n) = sum_{k <= n} chi(k). 3

%I

%S 0,1,2,2,3,3,4,4,4,5,5,5,6,6,6,6,7,7,7,8,8,8,8,8,8,9,9,10,10,10,10,10,

%T 11,11,12,12,12,12,12,12,13,13,14,14,15,15,15,15,16,16,16,17,17,17,17,

%U 17,18,18,18,19,19,19,19,20,20,20,20,20,21,21,21,21,21,21,21,21,21,21

%N Let chi(k) = 1 if prime(k+1) - prime(k) = 2, = 0 otherwise; sequence gives a(n) = sum_{k <= n} chi(k).

%F a(n)=A071538(A000040(n)). [From _R. J. Mathar_, Oct 06 2008]

%e n p D a(n) (p=prime(n), D = prime(n+1)-prime(n))

%e 1 2 1 0

%e 2 3 2 1

%e 3 5 2 2

%e 4 7 4 2

%e 5 11 2 3

%e 6 13 4 3

%Y Cf. A000040, A001223.

%K nonn

%O 1,3

%A Artemario Tadeu Medeiros da Silva (artemario(AT)uol.com.br), Apr 26 2003

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Last modified May 25 19:58 EDT 2019. Contains 323576 sequences. (Running on oeis4.)