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 A037156 10^n*(10^n+1)/2. 1
 1, 55, 5050, 500500, 50005000, 5000050000, 500000500000, 50000005000000, 5000000050000000, 500000000500000000, 50000000005000000000, 5000000000050000000000, 500000000000500000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Sum of first 10^n positive integers. - Omar E. Pol, May 03 2015 REFERENCES C. Pickover, Wonders of Numbers, Oxford University Press, NY, 2001, p. 328. LINKS Brian Hayes, Gauss's Day of Reckoning, American Scientist Bill Johnson, The great Gauss summation trick C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review FORMULA a(n) = A000533(n) * A093143(n). - Omar E. Pol, May 03 2015 From Chai Wah Wu, May 28 2016 : (Start) a(n) = 110*a(n-1) - 1000*a(n-2). G.f.: (1 - 55*x)/((10*x - 1)*(100*x - 1)). (End) EXAMPLE From Omar E. Pol, May 03 2015: (Start) For n = 0; a(0) = 1                       =    1 * 1   = 1 For n = 1; a(1) = 1 + 2 + ...... + 9 + 10 =   11 * 5   = 55 For n = 2; a(2) = 1 + 2 + .... + 99 + 100 =  101 * 50  = 5050 For n = 3; a(3) = 1 + 2 + .. + 999 + 1000 = 1001 * 500 = 500500 ... (End) CROSSREFS A subsequence of the triangular numbers A000217. Sequence in context: A119081 A119051 A119083 * A116110 A060204 A231783 Adjacent sequences:  A037153 A037154 A037155 * A037157 A037158 A037159 KEYWORD easy,nonn AUTHOR EXTENSIONS Corrected by T. D. Noe, Nov 07 2006 STATUS approved

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Last modified October 22 00:52 EDT 2019. Contains 328315 sequences. (Running on oeis4.)