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A027721

Palindromes of form k^2 + k + 6.

6, 8, 606, 656, 818, 83238, 6177716, 6505056, 8343438, 8681868, 834545438, 21543634512, 69872727896, 83456565438, 85425552458, 8032131312308, 8255470745528, 8345676765438, 8716172716178, 8766434346678, 8915858585198, 8973808083798, 213296020692312

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OFFSET

1,1

COMMENTS

Palindromes h such that 4*h - 23 is a square. - Bruno Berselli, Aug 29 2018

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..34

P. De Geest, Palindromic Quasi_Over_Squares of the form n^2+(n+X)

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 *)

Parallelize[Select[Table[n^2+n+6, {n, 0, 14605000}], PalindromeQ]] (* Harvey P. Dale, Nov 16 2025 *)

CROSSREFS

Cf. A027729, A027691, A027728, A027723.

Sequence in context: A295429 A267165 A000955 * A264518 A259129 A389860

Adjacent sequences: A027718 A027719 A027720 * A027722 A027723 A027724

KEYWORD

nonn,base

AUTHOR

Patrick De Geest

EXTENSIONS

More terms from Giovanni Resta, Aug 27 2018

STATUS

approved

URL: https://oeis.org/A027721

⇱ A027721 - OEIS