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 A215027 a(n+1) = (concatenation of n and n+1) - a(n), a(0) = 0. 3
 0, 1, 11, 12, 22, 23, 33, 34, 44, 45, 865, 146, 966, 247, 1067, 348, 1168, 449, 1269, 550, 1370, 651, 1471, 752, 1572, 853, 1673, 954, 1774, 1055, 1875, 1156, 1976, 1257, 2077, 1358, 2178, 1459, 2279, 1560, 2380, 1661, 2481, 1762, 2582, 1863, 2683, 1964, 2784, 2065, 2885, 2166, 2986, 2267, 3087, 2368, 3188, 2469, 3289, 2570, 3390, 2671, 3491, 2772, 3592, 2873, 3693 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Eric Angelini defined this by saying that "a(n)+a(n+1) = concatenation of n and (n+1)". An easy induction argument shows that a(n) is always positive. LINKS Table of n, a(n) for n=0..66. FORMULA The o.g.f. x*(1+10*x+810*x^9-720*x^10)/(1+x)/(1-x)^2 yields correct terms up to a(99), but not beyond. - M. F. Hasler, Aug 23 2012 EXAMPLE a(100) = concat(99,100) - a(99) = 99 100 - 4590 = 94510. MAPLE f:=proc(i) i*10^(1+floor(evalf(log10(i+1), 10)))+i+1; end: # A001704 a:=proc(n) option remember; global f; if n=1 then 1 else f(n-1)-a(n-1); fi; end; PROG (PARI) A215027(n, print_all=0)={my(a=print_all & print1(0)); for(n=1, n, a=(n-1)*10^#Str(n)+n-a; print_all & print1(", "a)); a} \\ - M. F. Hasler, Aug 23 2012 CROSSREFS Cf. A001704, A215028. Sequence in context: A101233 A118512 A112651 * A331194 A105945 A139114 Adjacent sequences: A215024 A215025 A215026 * A215028 A215029 A215030 KEYWORD nonn,base AUTHOR N. J. A. Sloane, Aug 04 2012, based on a posting to the Sequence Fans Mailing List by Eric Angelini. EXTENSIONS Initial term a(0)=0 added by M. F. Hasler, Aug 23 2012 STATUS approved

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Last modified February 29 17:04 EST 2024. Contains 370427 sequences. (Running on oeis4.)