A173665 Primes formed by the initial digits of the decimal expansion of 1/Catalan's constant.

109, 1091, 109174406370390610145415947333, 10917440637039061014541594733338923249860501214082473450059137

Offset

1,1

Comments

Primes found in 1/ A006752.

a(5) = 109174406...792972361 has 109 digits,

a(6) = 109174406...955798301 has 271 digits,

a(7) = 109174406...813410233 has 319 digits,

a(8) = 109174406...519744361 has 1223 digits.

Links

Table of n, a(n) for n=1..4.

Example

1/Catalan's constant = 1.09174406..., so a(1) = 109 ; a(2) = 1091.

Maple

Digits := 100; n0 := evalf(1/Catalan); for i from 1 to 100 do x := trunc(10^i*n0):
  if isprime(x) then printf(`%d, `, x): fi: od:

Prog

(PARI) default(realprecision, 350); C=intnum(t=0, 1, atan(t)/t); for(k=1, default(realprecision), ispseudoprime(10^k\C) && print(10^k\C, " digits: ", k+1)) \\ M. F. Hasler, Nov 24 2010

Crossrefs

Cf. A006752, A014538.

Sequence in context: A359144 A239720 A096214 * A059936 A262854 A232118

Adjacent sequences: A173662 A173663 A173664 * A173666 A173667 A173668

Keyword

nonn,base

Author

Michel Lagneau, Nov 24 2010

Status

approved