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

%I A198188 #13 Jan 27 2021 10:11:49
%S A198188 2,7,71,271,2,281,2718281,2,5,59,5,2,3,23,523,4523,904523,5,3,53,353,
%T A198188 8284590452353,2,7,360287,28459045235360287,7,47,8747,6028747,
%U A198188 8182845904523536028747,71,360287471,8281828459045235360287471,3,13,74713,82818284590452353602874713
%N A198188 Primes from the decimal expansion of e, sorted first by the final digit index and then by length.
%H A198188 M. F. Hasler, <a href="/A198188/b198188.txt">Table of n, a(n) for n = 1..655</a>
%e A198188 The first digit, 2, is prime, so a(1) = 2.
%e A198188 The second digit, 7, is prime, so a(2) = 7. 27 is not prime.
%e A198188 The third digit, 1, is not prime, but 71 and 271 are, so a(3) = 71 and a(4) = 271.
%e A198188 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
%o A198188 (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]
%o A198188 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", "))))
%o A198188 (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
%Y A198188 Cf. A095935.
%K A198188 nonn,base
%O A198188 1,1
%A A198188 _Franklin T. Adams-Watters_, Oct 21 2011