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 A260117 Smallest triangular number that is pandigital in base n. 5
 6, 15, 78, 990, 8385, 128271, 2293011, 46923828, 1062489753, 27403863105, 757016521030, 24028339652778, 807863408487460, 29499468896141965, 1162871296355724735, 49093065731151773880, 2200689210818047715703, 104755000778178115071015, 5271254575974180914006953 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 COMMENTS Presumably, lim_{n->infinity} a(n)/A049363(n) = 1. LINKS Chai Wah Wu, Table of n, a(n) for n = 2..28 (n = 2..22 from Jon E. Schoenfield) EXAMPLE Using the letters a, b, c, ... to represent digit values 10, 11, 12, ..., the terms are as follows: .    n            a(n) in base 10  a(n) in base n   ==  =========================  ==============    2                          6  110_2    3                         15  120_3    4                         78  1032_4    5                        990  12430_5    6                       8385  102453_6    7                     128271  1042653_7    8                    2293011  10576423_8    9                   46923828  107258346_9   10                 1062489753  1062489753_10   11                27403863105  10692847a53_11   12               757016521030  10286b37459a_12   13             24028339652778  1053b2a49c786_13   14            807863408487460  1036cb2487d59a_14   15          29499468896141965  102568d3be749ca_15   16        1162871296355724735  102359486ac7edbf_16   17       49093065731151773880  1029a46d78g53cbef_17   18     2200689210818047715703  10237c486geh5bdaf9_18   19   104755000778178115071015  10236a47589cgdfeibh_19   20  5271254575974180914006953  10235i96e4jb8gfcah7d_20 PROG (PARI) A049363(n)=if(n>1, (n^n-n)/(n-1)^2+n^(n-2)*(n-1)-1, 1) a(n)=my(k=ceil((sqrt(8*A049363(n)+1)-1)/2), t); while(#Set(digits(t=binomial(k+1, 2), n))

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Last modified June 24 20:34 EDT 2021. Contains 345425 sequences. (Running on oeis4.)