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 A084008 a(n) = T(n) concatenated with reverse(T(n)) divided by 11, where T(n) is the n-th triangular number. 2
 0, 1, 3, 6, 91, 141, 192, 262, 333, 414, 505, 606, 717, 829, 9591, 10911, 12421, 13941, 15561, 17281, 19092, 21012, 23032, 25152, 27273, 29593, 31923, 34443, 36964, 39594, 42324, 45154, 48075, 51015, 54145, 57276, 60606, 63937, 67377, 70917, 74548, 78288 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Table of n, a(n) for n=0..41. EXAMPLE a(12) = 7887/11 = 717. MAPLE a:= n-> (t-> parse(cat(t, (s-> seq(s[-i], i=1..length(s)))(""||t)))/11)(n*(n+1)/2): seq(a(n), n=0..50); # Alois P. Heinz, Nov 17 2018 MATHEMATICA r[n_] := FromDigits[Join[IntegerDigits[n], Reverse[IntegerDigits[n]]]]; Do[k = n*(n+1)/2; Print[r[k]/11], {n, 0, 50}] (* Ryan Propper, Sep 26 2005 *) f[n_]:=Module[{idn=IntegerDigits[n]}, FromDigits[Join[idn, Reverse[ idn]]] /11]; f/@Accumulate[Range[0, 40]] (* Harvey P. Dale, Sep 15 2011 *) CROSSREFS Cf. A000217, A004086. Sequence in context: A211896 A299433 A036286 * A092680 A101574 A082980 Adjacent sequences: A084005 A084006 A084007 * A084009 A084010 A084011 KEYWORD base,nonn AUTHOR Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 23 2003 EXTENSIONS More terms from Ryan Propper, Sep 26 2005 STATUS approved

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Last modified September 23 17:42 EDT 2023. Contains 365554 sequences. (Running on oeis4.)