A028336 Positive numbers k such that k*(k+1) is a palindrome.

1, 2, 16, 77, 538, 1621, 2457, 5291, 5313, 52008, 142401, 143498, 1610151, 1713543, 4670028, 5218983, 15137566, 15282411, 15814148, 47370058, 50702751, 142594226, 166691108, 1694576061, 2554554552, 25541432472, 47878213558, 77714915542, 155482156418

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• base

Comments

For additional terms, see the De Geest link.

Links

• P. De Geest, Palindromic pronic numbers of the form n(n+1)
• Eric Weisstein's World of Mathematics, Palindromic Number.
• Eric Weisstein's World of Mathematics, Pronic Number.

Crossrefs

Cf. A008509, A028337.

Programs

Mathematica

Select[Range[500000], PalindromeQ[#(#+1)] &] (* or *) Select[Range[50000], IntegerDigits[#(#+1)] == Reverse[ IntegerDigits[#(#+1)]] &] (* G. C. Greubel, Nov 24 2016 *)

PARI

isok(k) = my(d = digits(k*(k+1))); Vecrev(d) == d; \\ Michel Marcus, Nov 09 2017

Extensions

More terms from Jon E. Schoenfield, Nov 09 2017