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A077784 Palindromic wing primes (a.k.a. near-repdigit palindromes) of the form (10^a(n)-1)/3+2*10^[ a(n)/2 ]. 1
3, 5, 35, 159, 237, 325, 355, 371, 481, 1649, 3641, 4709 (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.

a(13) > 2*10^5. - Robert Price, Apr 03 2016

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..12.

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

Makoto Kamada, Prime numbers of the form 33...33533...33

Index entries for primes involving repunits.

FORMULA

a(n) = 2*A183175(n)+1.

EXAMPLE

a(n)=5 -> (10^5-1)/3+2*10^2 = 33533.

MATHEMATICA

Do[ If[ PrimeQ[(10^n + 6*10^Floor[n/2] - 1)/3], Print[n]], {n, 3, 4800, 2}] (* Robert G. Wilson v, Dec 16 2005 *)

CROSSREFS

Partial sums of S(n, x), for x=1...9: A021823, A000217, A027941, A061278, A089817, A053142, A092521, A076765, A092420.

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

Sequence in context: A173092 A057908 A120828 * A145640 A222496 A086158

Adjacent sequences:  A077781 A077782 A077783 * A077785 A077786 A077787

KEYWORD

more,nonn,base

AUTHOR

Patrick De Geest, Nov 16 2002

STATUS

approved

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Last modified September 23 20:33 EDT 2017. Contains 292391 sequences.