Search: id:A003555
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%I A003555
%S A003555 1,66,6216,617716,61732716,6172882716,617284382716,61728399382716,
%T A003555 6172839549382716,617283951049382716,61728395066049382716,
%U A003555 6172839506216049382716,617283950617716049382716
%N A003555 Sum{1,2,...,(10^n - 1)/9}, or (10^n -1)/9)((10^n -1)/9 +1)/2 (n-th term 
               is the middle 2(n-1) digits of the (n+9)-th term for n > 1).
%C A003555 Patterned, or almost palindromic, numbers obtained by modification of 
               "half-repdigit" numbers. a[n]=A*(((100^n-1)/9)+B*(10^n - 1)/9)/18, 
               where A=1, B=8-A=7. For example, n = 20: a[20] = 1111111111111111111188888888888888888888/
               18 = 61728395061728395066049382716049382716, an "almost-palindromic-number". 
               - Labos E. (labos(AT)ana.sote.hu), Oct 28 2004
%C A003555 n is "almost palindromic" if digitlist-Rev[digitlist], besides zeros, 
               contains +1 or -1 in "regular" positions. - Labos E. (labos(AT)ana.sote.hu), 
               Oct 28 2004
%t A003555 f[x_] := 1*((100^x-1)/9) + 7*(10^x-1)/9 Table[f[w], {w, 1, 20}]/18 - 
               Labos E. (labos(AT)ana.sote.hu), Oct 28 2004
%Y A003555 Cf. A098210, A099638.
%Y A003555 Sequence in context: A004998 A097316 A099639 this_sequence A093266 A127706 
               A167778
%Y A003555 Adjacent sequences: A003552 A003553 A003554 this_sequence A003556 A003557 
               A003558
%K A003555 nonn,base
%O A003555 1,2
%A A003555 Daniel Lawson (dlawson(AT)cats.ucsc.edu)
%E A003555 Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion 
               of Andrew Plewe, May 31 2007

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