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A196495 Smallest multidigit palindromic centered n-gonal number. 0

%I #23 Apr 25 2021 12:14:41

%S 15151,181,141,919,22,121,55,11,111,121,131,141,151,161,171,55,191,

%T 121,22,189949981,484,505,151,11311,757,16661,88,181,72727,33,1111111,

%U 10201,10501,757,2636362,17671,51715,121,616,36163,44,1856581,676,12256565221

%N Smallest multidigit palindromic centered n-gonal number.

%C Is it true that there is no term for n = 56? - _T. D. Noe_, Oct 03 2011

%C No, the smallest multidigit palindromic centered 56-gonal number is 14075098988989057041 with base 709000780. - _Patrick De Geest_, Apr 25 2021

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/centered.htm">Palindromic Centered Polygonal Numbers</a>

%H T. Trotter, <a href="http://trottermath.net/polygonal-numbers/">Polygonal numbers</a>

%e 15151 is the smallest palindromic centered triangular number.

%e 121 is the smallest palindromic centered 40-gonal number.

%t palin[n_] := Module[{d = IntegerDigits[n]}, d == Reverse[d]]; Table[n = 1; While[num = n*k*(n-1)/2 + 1; num < 10 || ! palin[num], n++]; num, {k, 3, 50}] (* _T. D. Noe_, Oct 03 2011 *)

%K nonn,base

%O 3,1

%A _Kausthub Gudipati_, Oct 03 2011

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)