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 A008953 a(n) is the leading digit of the n-th triangular number, n*(n+1)/2. 3
 1, 3, 6, 1, 1, 2, 2, 3, 4, 5, 6, 7, 9, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 8, 8, 9, 9, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS R. Zumkeller, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A000030(A000217(n)). - Reinhard Zumkeller, May 12 2010] MATHEMATICA Array[IntegerDigits[# (# + 1) / 2][[1]]&, 100] (* Vincenzo Librandi, Apr 12 2019 *) PROG (PARI) a(n) = digits(n*(n+1)/2)[1]; \\ Michel Marcus, Jun 20 2018 (MAGMA) [Intseq((n*(n+1) div 2))[#Intseq((n*(n+1) div 2))]: n in [1..100]]; // Vincenzo Librandi, Apr 12 2019 CROSSREFS Cf. A000030, A000217, A008954. - Reinhard Zumkeller, May 12 2010 Sequence in context: A142464 A177022 A325634 * A104611 A076790 A095693 Adjacent sequences:  A008950 A008951 A008952 * A008954 A008955 A008956 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified October 16 16:18 EDT 2019. Contains 328101 sequences. (Running on oeis4.)