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Search: id:A091781
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| A091781 |
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Beginning with 1, sum of all possible strings obtained as concatenation of previous (successive) terms. |
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+0
2
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| 1, 1, 13, 1252, 12396260, 1239500874377560, 12395008619813008676506120642920, 1239500861981300743700524626536099160068958504069412048965143360, 12395008619813007437005246265360867650603386910607355428445004411155507757831706\ 693304721638824892440620626536624708440686290240
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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a(n) is the sum of n(n+1)/2 such strings. a(n) has roughly 2^(n-1) decimal digits. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 26 2007
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EXAMPLE
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a(0) = 1 hence a(1) = 1, a(2) = (1)+(1)+ (11) = 13, a(3) = (1) +(1) +(13) + (11) + (113) + (1113)=1252.
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MAPLE
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A055642 := proc(n) if n <= 1 then 1 ; else ilog10(n)+ 1; fi ; end: Lcat := proc(L, i, j) local resul, k ; resul := 0 ; for k in op(i..j, L) do resul := resul*10^A055642(k)+k ; od ; RETURN(resul) ; end: A091781 := proc(nmax) local a, anxt, n, i, j; a := [1] ; for n from 1 to nmax do anxt := 0 ; for i from 1 to nops(a) do for j from i to nops(a) do anxt := anxt+Lcat(a, i, j) : od ; od ; a := [op(a), anxt] ; od; RETURN(a) ; end: A091781(9) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 26 2007
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CROSSREFS
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Cf. A091782.
Sequence in context: A128685 A076481 A128897 this_sequence A156641 A064962 A066457
Adjacent sequences: A091778 A091779 A091780 this_sequence A091782 A091783 A091784
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 17 2004
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EXTENSIONS
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a(4) and a(5) from Donald Sampson (marsquo(AT)hotmail.com), Sep 17 2004
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 26 2007
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