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%I #26 Nov 10 2017 15:13:04
%S 1,2,16,77,538,1621,2457,5291,5313,52008,142401,143498,1610151,
%T 1713543,4670028,5218983,15137566,15282411,15814148,47370058,50702751,
%U 142594226,166691108,1694576061,2554554552,25541432472,47878213558,77714915542,155482156418
%N Positive numbers k such that k*(k+1) is a palindrome.
%C For additional terms, see the De Geest link.
%H P. De Geest, <a href="http://www.worldofnumbers.com/consec.htm">Palindromic pronic numbers of the form n(n+1)</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PalindromicNumber.html">Palindromic Number.</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PronicNumber.html">Pronic Number.</a>
%t Select[Range[500000], PalindromeQ[#(#+1)] &] (* or *) Select[Range[50000], IntegerDigits[#(#+1)] == Reverse[ IntegerDigits[#(#+1)]] &] (* _G. C. Greubel_, Nov 24 2016 *)
%o (PARI) isok(k) = my(d = digits(k*(k+1))); Vecrev(d) == d; \\ _Michel Marcus_, Nov 09 2017
%Y Cf. A008509, A028337.
%K nonn,base
%O 1,2
%A _Patrick De Geest_
%E More terms from _Jon E. Schoenfield_, Nov 09 2017
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