A077795 Numbers k such that (10^k - 1)/9 + 8*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).

3, 9, 53, 375, 453, 1749, 26619, 68033, 85179

Offset: 1

Author

Patrick De Geest, Nov 16 2002

Keywords

• more
• nonn
• base

Comments

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

a(10) > 400000. - Robert Price, Jan 30 2025

Examples

			9 is a term because (10^9 - 1)/9 + 8*10^4 = 111191111.
		

References

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

Links

• Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
• Makoto Kamada, Prime numbers of the form 11...11911...11
• Index entries for primes involving repunits.

Crossrefs

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

Formula

a(n) = 2*A107649(n) + 1.

Extensions

Name corrected by Jon E. Schoenfield, Oct 30 2018

a(8)-a(9) from Robert Price, Jan 30 2025