A092696 - OEIS

A092696

Smoothly undulating palindromic primes of the form (12*10^n-21)/99.

1212121, 12121212121, 1212121212121212121212121212121212121212121

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OFFSET

1,1

COMMENTS

The De Geest link calls these smoothly undulating palindromic primes. Corresponding n are given in A062209. Equivalently, primes of the form 1212...121: Decimal digits "12" repeated k times with 1 appended (or "21" repeated k times with 1 prefixed). Corresponding k are given in A056803. The next term, a(4), has "12" repeating A056803(4) = 69 times and length A062209(4) = 2*A056803(4) + 1 = 139 decimal digits.

LINKS

Table of n, a(n) for n=1..3.

P. De Geest, SUPP Reference Table

Index entries for sequences related to smoothly undulating palindromic primes

FORMULA

a(n) = (4*10^A062209(n)-7)/33. - M. F. Hasler, Jul 30 2015

CROSSREFS

Cf. A056803 (number of 12's (or 21's)), A062209 (corresponding decimal digit lengths).

Cf. A032758, A033619, A030291, A059168, A242541, A004022.

Sequence in context: A251166 A274833 A206042 * A203627 A235910 A234997

Adjacent sequences: A092693 A092694 A092695 * A092697 A092698 A092699

KEYWORD

bref,nonn,base

AUTHOR

Rick L. Shepherd, Mar 04 2004

EXTENSIONS

Edited by M. F. Hasler, Jul 30 2015

STATUS

approved