A098826 Palindromes that are 1 more than a prime and 1 less than a triangular number.

44, 252, 434, 464, 4004, 46664, 2005002, 49099094, 414878414, 431313134, 4370654560734, 200000050000002, 417622181226714, 202837977779738202, 2574289191919824752

Offset

1,1

Links

Table of n, a(n) for n=1..15.

Example

a(1) = 44 because 44 is the smallest (first) palindrome that is 1 more than a prime (43) and 1 less than a triangular number (45).

Mathematica

Do[t = n(n + 1)/2 - 1; If[EvenQ[t], If[PrimeQ[t - 1], If[t == FromDigits[ Reverse[ IntegerDigits[ t]]], Print[t]]]], {n, 10^9}] (* _Robert G. Wilson v, Nov 04 2004 *)
Select[Accumulate[Range[227*10^7]]-1, PalindromeQ[#]&&PrimeQ[#-1]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 02 2020 *)

Crossrefs

Sequence in context: A233942 A122245 A031175 * A160284 A060836 A135182

Adjacent sequences: A098823 A098824 A098825 * A098827 A098828 A098829

Keyword

base,nonn

Author

Anonymous, Nov 02 2004

Status

approved