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 A104620 Consider the presentation of the digits of the natural numbers in a triangular form for successive bases, b. Now examine the main diagonal of these triangles and note the first occurrence of the n digits (0 through b-1). This is its own triangle presented here. 15
 1, 2, 1, 4, 1, 9, 6, 1, 8, 2, 3, 1, 4, 2, 19, 10, 1, 7, 2, 5, 31, 8, 1, 6, 2, 10, 18, 3, 14, 1, 7, 2, 11, 12, 3, 10, 4, 1, 29, 2, 8, 13, 3, 12, 62, 13, 1, 5, 2, 12, 6, 3, 9, 23, 73, 12, 1, 9, 2, 13, 11, 3, 16, 7, 80, 4, 22, 1, 8, 2, 6, 15, 3, 18, 19, 10, 4, 37, 11, 1, 9, 2, 13, 70, 3, 7, 26, 16 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS See A104606 through A104613, A091425, A104614 through A104619 as examples in the OEIS data base for triangular forms to base n>1. t(n,2)=1, t(n,4)=2, t(n,7)=3, t(n,11)=4, t(n,16)=5 and t(n,1+i(i+1)/2)=i. LINKS Table of n, a(n) for n=1..88. EXAMPLE Triangle begins: 1 2 1 4 1 9 6 1 8 2 3 1 4 2 19 10 1 7 2 5 31 MATHEMATICA f[n_] := If[n == 1, 0, Block[{t = Flatten[ IntegerDigits[ Range[ 2000], n]]}, u = t[[ Table[ i(i + 1)/2, {i, 100}]]]; Table[ Position[u, i, 1, 1], {i, 0, n - 1}]]]; Flatten[ Table[ f[n], {n, 13}]] CROSSREFS Cf. A104606, A104607, A104608, A104609, A104610, A104611, A104612, A104613, A091425, A104614, A104615, A104616, A104617, A104618, A104619. Sequence in context: A147080 A146418 A146011 * A243913 A186724 A145930 Adjacent sequences: A104617 A104618 A104619 * A104621 A104622 A104623 KEYWORD base,nonn,tabl AUTHOR Robert G. Wilson v, Mar 17 2005 STATUS approved

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Last modified June 4 09:19 EDT 2023. Contains 363121 sequences. (Running on oeis4.)