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

Author

Franklin T. Adams-Watters, Oct 21 2011

Keywords

• nonn
• base

Examples

			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
		

Links

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

Crossrefs

Cf. A095935.

Programs

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