A198188 Primes from the decimal expansion of e, sorted first by the final digit index and then by length.

2, 7, 71, 271, 2, 281, 2718281, 2, 5, 59, 5, 2, 3, 23, 523, 4523, 904523, 5, 3, 53, 353, 8284590452353, 2, 7, 360287, 28459045235360287, 7, 47, 8747, 6028747, 8182845904523536028747, 71, 360287471, 8281828459045235360287471, 3, 13, 74713, 82818284590452353602874713

Offset

1,1

Links

M. F. Hasler, Table of n, a(n) for n = 1..655

Example

The first digit, 2, is prime, so a(1) = 2.
The second digit, 7, is prime, so a(2) = 7. 27 is not prime.
The third digit, 1, is not prime, but 71 and 271 are, so a(3) = 71 and a(4) = 271.
a(17) shows that "leading zeros are not allowed", i.e., if a prime p is prefixed by a 0 then it is not listed twice. - M. F. Hasler, Feb 05 2012

Prog

(PARI) v=[2, 7, 1, 8, 2, 8, 1, 8, 2, 8, 4, 5, 9, 0, 4, 5, 2, 3, 5, 3, 6, 0, 2, 8, 7, 4, 7, 1, 3]
for(n=1, #v, x=0; p=1; forstep(k=n, 1, -1, x+=p*v[k]; p*=10; if(v[k]&&isprime(x), print1(x", "))))
(PARI) default(realprecision, D=300); for(i=0, D-5, E=exp(1)\.1^i; for(j=1, i+1, ispseudoprime(t=E%10^j) & t!=L print1(L=t", ")))  \\ M. F. Hasler, Feb 05 2012

Crossrefs

Cf. A095935.

Sequence in context: A165978 A106917 A188665 * A230459 A267406 A100360

Adjacent sequences: A198185 A198186 A198187 * A198189 A198190 A198191

Keyword

nonn,base

Author

Franklin T. Adams-Watters, Oct 21 2011

Status

approved