A260117 Smallest triangular number that is pandigital in base n.

6, 15, 78, 990, 8385, 128271, 2293011, 46923828, 1062489753, 27403863105, 757016521030, 24028339652778, 807863408487460, 29499468896141965, 1162871296355724735, 49093065731151773880, 2200689210818047715703, 104755000778178115071015, 5271254575974180914006953

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))<n, k++); t \\ Charles R Greathouse IV, Jul 17 2015

Crossrefs

Cf. A049363.

Sequence in context: A108540 A232170 A165570 * A220360 A096565 A013229

Adjacent sequences: A260114 A260115 A260116 * A260118 A260119 A260120

Keyword

nonn,base

Author

Jon E. Schoenfield, Jul 17 2015

Status

approved