OFFSET

1,1

COMMENTS

Leading zeros are not permitted, i.e., all terms must be two digits in length. - Harvey P. Dale, Apr 20 2012

The last of the 21 2-digit primes to appear is a(233) = 19. - Charles R Greathouse IV, May 13 2019

LINKS

Harvey P. Dale and Vincenzo Librandi, Table of n, a(n) for n = 1..1001

The first 15,000 digits of Cos(1) as calculated by Simon Plouffe at WorldWideSchool.org.

Eric Weisstein's World of Mathematics, Cosine Function

MATHEMATICA

Select[FromDigits/@Partition[RealDigits[Cos[1], 10, 400][[1]], 2, 1], PrimeQ[#]&&#>9&] (* Harvey P. Dale, Apr 20 2012 *)

CROSSREFS

KEYWORD

nonn,base

AUTHOR

Andrew G. West (WestA(AT)wlu.edu), Mar 30 2005

EXTENSIONS

Offset changed from 0 to 1 by Vincenzo Librandi, Apr 28 2013

STATUS

approved