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A138301 Number of integers k < 10^n such that k*(k+1)-1 and k*(k+3)-1 are both first of twin primes. 0
1, 2, 4, 11, 37, 145, 673, 3748, 22875 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

3*4-1=11 11 and 13 twin primes, 3*6-1=17 17 and 19 twin primes a(1)=1

15*16-1=239 239 and 241 twin primes, 15*18-1=269 269 and 271 twin primes a(2)=2

CROSSREFS

Cf. A138303.

Sequence in context: A174107 A253927 A281481 * A173939 A328433 A118182

Adjacent sequences:  A138298 A138299 A138300 * A138302 A138303 A138304

KEYWORD

nonn

AUTHOR

Pierre CAMI, Mar 14 2008

STATUS

approved

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Last modified June 6 17:28 EDT 2020. Contains 334830 sequences. (Running on oeis4.)