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

1,2

Comments

Multiplicative analog of A060403.

Links

Table of n, a(n) for n=1..10.

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)).

Example

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.

Sequence in context: A118750 A070826 A048599 * A269455 A088109 A231634

Adjacent sequences: A129728 A129729 A129730 * A129732 A129733 A129734

Keyword

easy,nonn,word,dumb,less

Author

Jonathan Vos Post, May 12 2007, May 22 2007

Status

approved