A077776 Numbers k such that (10^k - 1) - 8*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).

3, 11, 27, 87, 339, 363, 3159, 36155, 45305, 314727

Offset

1,1

Comments

Prime versus probable prime status and proofs are given in the author's table.

References

C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

Links

Table of n, a(n) for n=1..10.

Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)

Makoto Kamada, Prime numbers of the form 99...99199...99

Index entries for primes involving repunits.

Formula

a(n) = 2*A183184(n) + 1.

Example

27 is a term because (10^27 - 1) - 8*10^13 = 999999999999919999999999999.

Mathematica

Do[ If[ PrimeQ[10^n - 8*10^Floor[n/2] - 1], Print[n]], {n, 3, 1000, 2}] (* Robert G. Wilson v, Dec 16 2005 *)

Crossrefs

Cf. A004023, A077775-A077798, A107123-A107127, A107648, A107649, A115073, A183174-A183187.

Sequence in context: A250223 A250271 A289842 * A113836 A036571 A003060

Adjacent sequences: A077773 A077774 A077775 * A077777 A077778 A077779

Keyword

more,nonn,base

Author

Patrick De Geest, Nov 16 2002

Extensions

One more term from PWP table added by Patrick De Geest, Nov 05 2014

Name corrected by Jon E. Schoenfield, Oct 31 2018

Status

approved