A087402 a(n) is the smallest repdigit > 10 such that Sum_{i=0..n} a(i) is prime.

11, 222, 44, 222, 22, 66, 44, 22, 66, 222, 222, 66, 222, 888, 44, 666, 88, 44, 22, 888, 66, 44, 88, 444, 66, 222, 66, 66, 44, 222, 22, 66, 66, 66, 44, 66, 888, 22, 44, 88, 66, 222, 444, 66, 2222, 22, 666, 2222, 22, 66, 44, 66, 22, 66, 222, 222, 6666, 44, 22, 66, 444, 66

Offset

0,1

Comments

The total of the first 992 terms (from a(0) to a(991)) is a prime with 1247 digits. The largest term among the first 992 terms is a(920), which also has 1247 digits. If a(992) exists, it has more than 1251 digits. - Harvey P. Dale, Sep 03 2023

Links

Harvey P. Dale, Table of n, a(n) for n = 0..992

Example

11, 11+222=233, 11+222+44=277 etc. are all prime.

Mathematica

nxt[{t_, n_}]:=Module[{tbl=LinearRecurrence[{0, 0, 0, 11, 0, 0, 0, -10}, {22, 44, 66, 88, 222, 444, 666, 888}, 20], c}, c= SelectFirst[tbl, PrimeQ[t+#]&]; {t+c, c}]; NestList[nxt, {11, 11}, 70][[;; , 2]] (* Harvey P. Dale, Sep 03 2023 *)

Crossrefs

Sequence in context: A055411 A341491 A064093 * A048377 A192686 A323416

Adjacent sequences: A087399 A087400 A087401 * A087403 A087404 A087405

Keyword

base,nonn

Author

Amarnath Murthy, Sep 10 2003

Extensions

More terms from Ray Chandler and Vladeta Jovovic, Sep 22 2003

New name from David A. Corneth, Sep 03 2023

Status

approved