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 A066547 Let N = 123456789101112131415161718..., the concatenation of the natural numbers. a(n) is the n-digit number formed from the digits of N starting from the {n(n-1)/2 +1}th digit. Omit any leading zeros. 11
 1, 23, 456, 7891, 1112, 131415, 1617181, 92021222, 324252627, 2829303132, 33343536373, 839404142434, 4454647484950, 51525354555657, 585960616263646, 5666768697071727, 37475767778798081, 828384858687888990, 9192939495969798991, 101102103104105106, 107108109110111112113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..71 EXAMPLE 1, 23, 456, 7891, 01112, 131415, 1617181, 92021222, 3... becomes 1, 23, 456, 7891, 1112, 131415, 1617181, 92021222, ... MATHEMATICA d = Flatten[IntegerDigits /@ Range[90]]; Table[FromDigits[Take[d, {n(n + 1)/2 + 1, (n + 1)(n + 2)/2}]], {n, 0, 17}] (* Robert G. Wilson v, Nov 22 2004 *) PROG (PARI) N=[]; k=0; for(n=1, 20, while(#N

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Last modified December 8 12:03 EST 2022. Contains 358693 sequences. (Running on oeis4.)