login
This site is supported by donations to The OEIS Foundation.

 

Logo

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A008509 Numbers n such that n-th triangular number is palindromic. 12
1, 2, 3, 10, 11, 18, 34, 36, 77, 109, 132, 173, 363, 1111, 1287, 1593, 1833, 2662, 3185, 3369, 3548, 8382, 11088, 18906, 50281, 57166, 102849, 111111, 167053, 179158, 246642, 337650, 342270, 365436, 417972, 1620621, 3240425, 3457634, 3707883 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Charles W. Trigg, Palindromic Triangular Numbers, J. Rec. Math., 6 (1973), 146-147.

D. Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, 93.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..147 (from P. De Geest)

P. De Geest, Palindromic Triangulars

MATHEMATICA

palQ[n_]:= Reverse[x=IntegerDigits[n]]==x; t={}; Do[If[palQ[n*(n+1)/2], AppendTo[t, n]], {n, 4*10^6}]; t (* Jayanta Basu, May 13 2013 *)

PROG

(PARI) ispal(n)=n=digits(n); for(i=1, #n\2, if(n[i]!=n[#n+1-i], return(0))); 1

is(n)=ispal(n*(n+1)/2) \\ Charles R Greathouse IV, May 15 2013

CROSSREFS

Cf. A003098, A002113, A000217, A083571, A050721, A050722.

Sequence in context: A248407 A047473 A270474 * A281366 A081868 A212103

Adjacent sequences:  A008506 A008507 A008508 * A008510 A008511 A008512

KEYWORD

nonn,base

AUTHOR

Patrick De Geest

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 20 13:04 EDT 2017. Contains 290835 sequences.