A130664 a(1)=1. a(n) = a(n-1) + (number of terms from among a(1) through a(n-1) which are factorials).

1, 2, 4, 6, 9, 12, 15, 18, 21, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96, 100, 104, 108, 112, 116, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250

Offset: 1

Author

Leroy Quet, Jun 21 2007

Keywords

• easy
• nonn

Comments

Also this is an irregular array where row n contains the n! consecutive multiples of n starting with n!.

For n >= 1, (a(n), A084555(n)) = (1,1), (2,3), (4,5), (6,8), (9,11), (12,14), ... gives the starting and ending offsets of the n-th permutation in the sequences like A030298 and A030496. Gives also the fixed points of A220662; we have A220662(a(n)) = a(n). - Antti Karttunen, Dec 18 2012

Examples

			When interpreted as an irregular table, the rows begin as:
  1;
  2, 4;
  6, 9, 12, 15, 18, 21;
		

Links

• Antti Karttunen, Rows 1..7 of irregular table, flattened.

Crossrefs

Cf. A000142, A084555, A220662.

Programs

Maple

A[1]:= 1:
nextf:= 2!:
m:= 1:
for n from 2 to 100 do
  A[n]:= A[n-1]+m;
  if A[n] = nextf then
     m:= m+1;
      nextf:= (m+1)!;
  fi;
od:
seq(A[i],i=1..100); # Robert Israel, Apr 28 2016

Mathematica

Table[Range[n!, (n + 1)! - 1, n], {n, 5}] // Flatten (* Michael De Vlieger, Aug 29 2017 *)

Scheme

(define (A130664 n) (+ 1 (A084555(- n 1))))

Formula

a(n) = A084555(n-1) + 1.