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A027721
Palindromes of form k^2 + k + 6.
4
6, 8, 606, 656, 818, 83238, 6177716, 6505056, 8343438, 8681868, 834545438, 21543634512, 69872727896, 83456565438, 85425552458, 8032131312308, 8255470745528, 8345676765438, 8716172716178, 8766434346678, 8915858585198, 8973808083798, 213296020692312
OFFSET
1,1
COMMENTS
Palindromes h such that 4*h - 23 is a square. - Bruno Berselli, Aug 29 2018
FORMULA
a(n) = A027729(n)^2 + A027729(n) + 6. - Giovanni Resta, Aug 27 2018
MATHEMATICA
palQ[n_] := Block[{d = IntegerDigits[n]}, d == Reverse[d]]; f[n_] := n^2 + n + 6; Select[f@ Range[0, 10^5], palQ] (* Giovanni Resta, Aug 29 2018 *)
CROSSREFS
KEYWORD
nonn,base
EXTENSIONS
More terms from Giovanni Resta, Aug 27 2018
STATUS
approved