A129731 Each term is the previous term times the number of letters in the previous number, as conventionally spelled out in English.

1, 3, 15, 105, 1470, 42630, 1364160, 75028800, 3676411200, 272054428800

Offset: 1

Author

Jonathan Vos Post, May 12 2007, May 22 2007

Keywords

• easy
• nonn
• word
• dumb
• less

Comments

Multiplicative analog of A060403.

Examples

			a(1) = 1.
a(2) = 1 * A060403(1) = 1 * LettersIn("one") = 1*3 = 3.
a(3) = 3 * A060403(2) = 3 * LettersIn("three") = 3*5 = 15.
a(4) = 15 * A060403(3) = 15 * LettersIn("fifteen") = 15*7 = 105.
a(10) = 74 * A060403(a(9)) = 74 * LettersIn("three billion six hundred seventysix million four hundred eleven thousand two hundred") = 1364160 * 55 * 49 * 74 = 272054 28800 = 2^7 * 3 * 5^2 * 7^4 * 11 * 29 * 37.
		

Crossrefs

Cf. A005589, A060403.

Formula

a(0) = 1; a(n+1) = a(n) * A005589(a(n)). a(0) = 1; a(n+1) = PRODUCT[i=1..n] A005589(a(i)).