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A109859
Number of terms of A109858 with digit sum n.
1
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
CROSSREFS
Cf. A109858.
Sequence in context: A086442 A071407 A309094 * A128057 A128014 A135401
KEYWORD
base,hard,nonn
AUTHOR
Amarnath Murthy, Jul 08 2005
EXTENSIONS
More terms from Joshua Zucker, May 05 2006
STATUS
approved