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A199322 Number of twin prime numbers of the form n*(n+1) + 2*k-3 and n*(n+1) + 2*k-1 with k = 1 to n+1. 1
1, 1, 2, 0, 1, 1, 1, 1, 2, 0, 2, 1, 2, 1, 2, 1, 1, 1, 0, 2, 1, 1, 1, 3, 1, 0, 1, 3, 1, 0, 3, 2, 1, 1, 4, 0, 2, 2, 2, 2, 2, 2, 2, 2, 5, 1, 3, 1, 0, 2, 4, 2, 0, 2, 2, 3, 4, 3, 3, 2, 2, 4, 4, 5, 1, 4, 2, 3, 2, 3, 1, 1, 5, 3, 2, 2, 2, 3, 2, 2, 6, 4, 1, 2, 3, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

0.66*n/log(n)^2 is a good approximation for a(n) as n increases

LINKS

Pierre CAMI, Table of n, a(n) for n = 1..10000

MATHEMATICA

Table[m = n*(n+1); Length[Select[Range[n+1], PrimeQ[m + 2*#-3] && PrimeQ[m + 2*#-1] &]], {n, 100}] (* T. D. Noe, Nov 07 2011 *)

CROSSREFS

Cf. A199323, A199324.

Sequence in context: A025905 A115861 A282355 * A284203 A005087 A050332

Adjacent sequences:  A199319 A199320 A199321 * A199323 A199324 A199325

KEYWORD

nonn

AUTHOR

Pierre CAMI, Nov 07 2011

STATUS

approved

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Last modified October 15 22:47 EDT 2018. Contains 316252 sequences. (Running on oeis4.)