OFFSET
1,1
COMMENTS
Is there a nonzero term beyond a(5)?
LINKS
P. De Geest, Palindromic Squares
Eric Weisstein's World of Mathematics, Palindromic Number
EXAMPLE
There is only one palindromic pentagonal number of length 4 whose index is also palindromic, 44->2882. Thus, a(4)=1.
MATHEMATICA
A002069 = {0, 1, 5, 22, 1001, 2882, 15251, 720027, 7081807, 7451547, 26811862, 54177145, 1050660501, 1085885801, 1528888251, 2911771192, 2376574756732, 5792526252975, 5875432345785, 10810300301801, 264571020175462, 5292834004382925, 10808388588380801, 15017579397571051, 76318361016381367, 150621384483126051, 735960334433069537, 1003806742476083001, 1087959810189597801, 2716280733370826172};
A028386 = {0, 1, 2, 4, 26, 44, 101, 693, 2173, 2229, 4228, 6010, 26466, 26906, 31926, 44059, 1258723, 1965117, 1979130, 2684561, 13280839, 59401650, 84885761, 100058581, 225563533, 316882086, 700457153, 818049201, 851649306, 1345679688};
CROSSREFS
KEYWORD
nonn,base,hard,more
AUTHOR
Robert Price, Apr 26 2019
EXTENSIONS
a(19)-a(35) from Chai Wah Wu, Sep 07 2019
STATUS
approved