A088061 a(1) = 11, a(n) = smallest prime obtained by starting with a(n-1) and prefixing it with one or more copies of (the decimal expansion of) n.

11, 211, 33211, 44433211, 5544433211, 65544433211, 77777777777765544433211

Offset

1,1

Comments

Next term has 657 digits and is too large to include. - David Wasserman, Jul 01 2005

a(9) has 1280 digits: 623 repeats of "9" + 634 repeats of "8" + 12 repeats of "7" + "65544433211". a(10) has 4990 digits: 1855 repeats of "10" + a(9). a(8), a(9), a(10) are verified by PARI ispseudoprime function. - Dmitry Petukhov, Oct 15 2017

Links

Table of n, a(n) for n=1..7.

Example

a(3) = 33211 as 3211 is not a prime but 33211 is.

Prog

(PARI) x=0; n=-1; for(k=1, 9, z=n; while(1, n++; x=x+k*10^n; if(ispseudoprime(x), print(x); break))) \\ Dmitry Petukhov, Oct 15 2017

Crossrefs

Cf. A088062.

Sequence in context: A112704 A243674 A114758 * A070220 A134069 A137464

Adjacent sequences: A088058 A088059 A088060 * A088062 A088063 A088064

Keyword

base,nonn

Author

Amarnath Murthy, Sep 21 2003

Status

approved