

A077791


Palindromic wing primes (a.k.a. nearrepdigit palindromes) of the form (10^a(n)1)/9+7*10^[ a(n)/2 ].


1




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, 199697, pp. 19.


LINKS

Table of n, a(n) for n=1..8.
Patrick De Geest, World!Of Numbers, Palindromic Wing Primes (PWP's)
Makoto Kamada, Prime numbers of the form 11...11811...11
Index entries for primes involving repunits.


FORMULA

a(n) = 2*A107648(n)+1.


EXAMPLE

a(n)=13 > (10^131)/9+7*10^6 = 1111118111111.


MATHEMATICA

Do[ If[ PrimeQ[(10^n + 63*10^Floor[n/2]  1)/9], Print[n]], {n, 3, 6400, 2}] (from Robert G. Wilson v, Dec 16 2005)


CROSSREFS

Cf. A004023, A077775A077798, A107123A107127, A107648, A107649, A115073, A183174A183187.
Sequence in context: A111230 A046865 A063791 * A176393 A240108 A163595
Adjacent sequences: A077788 A077789 A077790 * A077792 A077793 A077794


KEYWORD

more,nonn,base


AUTHOR

Patrick De Geest, Nov 16 2002.


STATUS

approved



