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A078891 Concatenate first n triangular numbers in reverse order. 1
1, 31, 631, 10631, 1510631, 211510631, 28211510631, 3628211510631, 453628211510631, 55453628211510631, 6655453628211510631, 786655453628211510631, 91786655453628211510631, 10591786655453628211510631, 12010591786655453628211510631 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

Shyam Sunder Gupta, Smarandache Sequence of Triangular Numbers, Smarandache Notions Journal, (to appear in Vol. 14, 2003).

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

a(3)=631 because 6,3,1 are first 3 triangular numbers in reverse order.

MAPLE

a:= proc(n) a(n):= `if`(n=1, 1, parse(cat(n*(n+1)/2, a(n-1)))) end:

seq(a(n), n=1..20);  # Alois P. Heinz, Jan 13 2021

MATHEMATICA

Table[FromDigits[Flatten[IntegerDigits[Table[n*(n+1)/2, {n, m, 1, -1}]]]], {m, 1, 20}]

CROSSREFS

Cf. A000217.

Sequence in context: A028013 A028073 A089758 * A078914 A068147 A025009

Adjacent sequences:  A078888 A078889 A078890 * A078892 A078893 A078894

KEYWORD

base,easy,nonn,less

AUTHOR

Shyam Sunder Gupta, Jan 10 2003

STATUS

approved

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Last modified June 28 21:04 EDT 2022. Contains 354907 sequences. (Running on oeis4.)