A109859 Number of terms of A109858 with digit sum n.

1, 2, 2, 6, 6, 20, 20, 70, 70, 251, 251, 918, 917, 3404, 3396, 12750, 12705, 48125, 47905, 182735, 181743, 697193, 692924, 2670538, 2652676, 10263255, 10189830, 39554920, 39256570, 152819066, 151616215, 591672286, 586848959, 2295096732

Offset

0,2

Comments

Can someone find a formula for the n-th term?

At first a(2n) = a(2n+1) because the palindromes of sum 2n can be placed into one-to-one correspondence with the palindromes of sum 2n+1 by inserting a 1 in the middle (if the number of digits is even) or adding one to the middle digit (if the number of digits is odd). However once there exists a palindrome with middle digit 9, this strategy no longer works. - Joshua Zucker, May 05 2006

Links

Table of n, a(n) for n=0..33.

Crossrefs

Cf. A109858.

Sequence in context: A086442 A071407 A309094 * A128057 A128014 A135401

Adjacent sequences: A109856 A109857 A109858 * A109860 A109861 A109862

Keyword

base,hard,nonn

Author

Amarnath Murthy, Jul 08 2005

Extensions

More terms from Joshua Zucker, May 05 2006

Status

approved