A034307 Numbers n such that there are no oblong (promic) palindromes of length n.
2, 5, 9, 12, 18, 20, 30, 34
Offset: 1
Links
- P. De Geest, Palindromic pronic numbers of the form n(n+1)
This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
Select[Range[500000], PalindromeQ[#(#+1)] &] (* or *) Select[Range[50000], IntegerDigits[#(#+1)] == Reverse[ IntegerDigits[#(#+1)]] &] (* G. C. Greubel, Nov 24 2016 *)
isok(k) = my(d = digits(k*(k+1))); Vecrev(d) == d; \\ Michel Marcus, Nov 09 2017
palQ[n_] := Block[{d = IntegerDigits[n]}, d == Reverse[d]]; f[n_] := n^2 + n + 1; Select[f@ Range[0, 10^5], palQ] (* Giovanni Resta, Aug 29 2018 *)
Comments