A098045 a(n) is the substring of the digits of A082521(n) that precedes the 2n+1 central zeros.

1, 13, 14, 19, 13, 14, 16, 71, 34, 35, 74, 94, 13, 13, 127, 94, 79, 106, 76, 74, 140, 14, 172, 118, 32, 73, 134, 71, 173, 395, 71, 14, 185, 115, 182, 97, 118, 13, 137, 104, 310, 31, 923, 701, 163, 152, 79, 115, 94, 17, 118, 73, 94, 349, 170, 17, 328, 158, 92, 944

Offset

0,2

Comments

I interpret A082521 to mean that A082521(n) has at least 2n+1 central zeros. If we require exactly 2n+1 central zeros, then a(21) is 329 instead of 140, a(41) is 328 instead of 310 and a(55) is 182 instead of 170.

Links

Jeppe Stig Nielsen, Table of n, a(n) for n = 0..800

Prog

(PARI) a(n)=forstep(j=10^(n+1), +oo, 10^(n+1), d=digits(j); p=fromdigits(vector(2*#d-1, k, if(k<#d, d[k], d[2*#d-k]))); ispseudoprime(p)&&return(j/10^(n+1))) \\ Jeppe Stig Nielsen, Apr 07 2025

Crossrefs

Sequence in context: A241749 A385364 A388076 * A293817 A360097 A360258

Adjacent sequences: A098042 A098043 A098044 * A098046 A098047 A098048

Keyword

base,easy,nonn,less

Author

David Wasserman, Sep 10 2004

Status

approved