A114996 a(n) = smallest palindrome > a(n-1) (for n > 0) such that the sum of its prime digits is equal to palindrome with index n, or -1 if none exists.

0, -1, 2, 3, 22, 151, 222, 232, 323, 333, 353, 37273, 77577, 7772777, 377777773, 5777777775, 77777777777, 27777777777772, 577777757777775, 577777777777775, 37777777777777773, 2777777775777777772, 7777777775777777777

Offset

0,3

Comments

Palindrome with index n is A002113(n).

Links

Table of n, a(n) for n=0..22.

Example

a(0) = 0 since A002113(0) = 0 and the prime digits of 0 sum to 0.
a(1) = -1 since A002113(1) = 1 and there is no number (all the more no palindrome) whose prime digits sum to 1.
a(5) = 151 since A002113(5) = 5 and 151 is the smallest palindrome > a(4) = 22 whose prime digits sum to 5.

Crossrefs

Cf. A002113.

Sequence in context: A264696 A166122 A366405 * A153256 A137077 A046965

Adjacent sequences: A114993 A114994 A114995 * A114997 A114998 A114999

Keyword

base,sign

Author

Giovanni Teofilatto, Feb 23 2006

Extensions

Edited, corrected and extended by Klaus Brockhaus, Mar 13 2006

a(16) and a(19) corrected, a(21) and a(22) added by Klaus Brockhaus, May 23 2007

Status

approved