OFFSET
1,2
COMMENTS
It is conjectured that a(n) grows like n^2/6.
REFERENCES
Popular Computing (Calabasas, CA), Z-Sequences, Vol. 4 (No. 42, Sep 1976), pp. 12-16.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
Popular Computing (Calabasas, CA), Z-Sequences, continued. Annotated and scanned copy of pages 14, 15, 16, 18 of Vol. 5 (No. 56, Nov 1977).
MAPLE
b:= proc(n) option remember;
`if`(n<3, 1, abs(b(n-1)+2*b(n-2)-n))
end:
a:= proc(n) option remember;
b(n)+`if`(n>1, a(n-1), 0)
end:
seq(a(n), n=1..60); # Alois P. Heinz, Apr 16 2015
MATHEMATICA
Accumulate[RecurrenceTable[{a[1] == a[2] == 1, a[n] == Abs[a[n-1] + 2a[n-2] - n]}, a, {n, 1, 100}]] (* Jean-François Alcover, Nov 23 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 16 2015
STATUS
approved