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 A062273 a(n) is an n-digit number with digits in increasing order with 0 following 9 and this is maintained in the concatenation of any number of consecutive terms. 8
 1, 23, 456, 7890, 12345, 678901, 2345678, 90123456, 789012345, 6789012345, 67890123456, 789012345678, 9012345678901, 23456789012345, 678901234567890, 1234567890123456, 78901234567890123, 456789012345678901, 2345678901234567890, 12345678901234567890 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is congruent to A000217(n), mod 10; i.e., the last digit of a(n) is the same as the last digit of the n-th triangular number, base 10 (A008954). - Carl R. White, Oct 21 2009 LINKS Robert Israel, Table of n, a(n) for n = 1..999 FORMULA From Carl R. White, Oct 21 2009: (Start) a(n) = floor( 10^(10*ceiling(n/10) + (n*(n+1)/2 mod 10)) * 1234567890/9999999999 ) mod 10^n. The generalized form g, for any integer base b (>2), is: g(b,n) = floor( b^(b*ceiling(n/b) + (n*(n+1)/2 mod b)) * floor( b^(b+1)/(b-1)^2 - (b+1) ) / (b^b-1)) mod b^n, so here a(n) = g(10,n). (End) a(n) = Sum_{i=1..n} ((n*(n-1)/2+i) mod 10)*10^(n-i). - Vedran Glisic, Apr 08 2011 EXAMPLE a(5) = 12345 as a(4) is 7890. MAPLE f:= proc(n) option remember: local d, t, k; d:= procname(n-1) mod 10; t:= 0: for k from 1 to n do d:= d+1 mod 10; t:= t + d*10^(n-k) od: t end proc: f(1):= 1: map(f, [\$1..30]); # Robert Israel, Apr 02 2018 MATHEMATICA FromDigits/@Table[Take[PadRight[{}, 250, Join[Range[9], {0}]], {(n(n+1))/2+ 1, ((n+1)(n+2))/2}], {n, 0, 20}] (* Harvey P. Dale, May 15 2015 *) PROG (PARI) a(n) = sum(i=1, n, ((n*(n-1)/2+i) % 10)*10^(n-i)); \\ Michel Marcus, May 26 2022 (Python) def a(n): return sum((n*(n-1)//2+i)%10*10**(n-i) for i in range(1, n+1)) print([a(n) for n in range(1, 21)]) # Michael S. Branicky, May 26 2022 after Michel Marcus CROSSREFS Cf. A000217, A008954. Sequence in context: A174262 A174425 A076068 * A066547 A001369 A007923 Adjacent sequences: A062270 A062271 A062272 * A062274 A062275 A062276 KEYWORD nonn,base,easy AUTHOR Amarnath Murthy, Jun 17 2001 EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), Jun 18 2001 STATUS approved

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Last modified June 10 04:13 EDT 2023. Contains 363187 sequences. (Running on oeis4.)