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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). 2
3, 9, 53, 375, 453, 1749, 26619 (list; graph; refs; listen; history; text; internal format)
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..7.

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.

FORMULA

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

EXAMPLE

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

CROSSREFS

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

Sequence in context: A018477 A226931 A013341 * A038496 A175596 A261397

Adjacent sequences:  A077792 A077793 A077794 * A077796 A077797 A077798

KEYWORD

more,nonn,base

AUTHOR

Patrick De Geest, Nov 16 2002

EXTENSIONS

Name corrected by Jon E. Schoenfield, Oct 30 2018

STATUS

approved

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Last modified September 27 06:31 EDT 2021. Contains 347673 sequences. (Running on oeis4.)