A038457 |First digit-last digit| for triangular numbers.

0, 0, 0, 0, 1, 4, 1, 6, 3, 1, 0, 0, 1, 8, 4, 1, 5, 2, 0, 1, 2, 1, 1, 4, 3, 2, 2, 5, 2, 1, 1, 2, 3, 4, 0, 6, 0, 4, 6, 7, 8, 7, 6, 3, 9, 4, 0, 7, 5, 4, 4, 5, 7, 0, 4, 1, 5, 2, 0, 1, 1, 0, 2, 4, 2, 3, 1, 6, 4, 3, 3, 4, 6, 1, 3, 2, 4, 0, 2, 3, 3, 2, 0, 3, 3, 2, 2, 5, 3, 1, 1, 2, 4, 3, 1, 4, 2, 1, 3, 4, 5

Offset

0,6

Links

Table of n, a(n) for n=0..100.

Formula

a(n) = A040163(A000217(n)). - Michel Marcus, Sep 27 2013

Mathematica

Abs[IntegerDigits[#][[1]]-IntegerDigits[#][[-1]]]&/@Accumulate[ Range[ 0, 120]] (* Harvey P. Dale, Mar 22 2020 *)

Crossrefs

Cf. A000217.

Sequence in context: A098987 A174390 A153017 * A141649 A101347 A200344

Adjacent sequences: A038454 A038455 A038456 * A038458 A038459 A038460

Keyword

easy,nonn,base

Author

Felice Russo

Status

approved