|
| |
|
|
A072668
|
|
Numbers one less than composite numbers.
|
|
8
| |
|
|
3, 5, 7, 8, 9, 11, 13, 14, 15, 17, 19, 20, 21, 23, 24, 25, 26, 27, 29, 31, 32, 33, 34, 35, 37, 38, 39, 41, 43, 44, 45, 47, 48, 49, 50, 51, 53, 54, 55, 56, 57, 59, 61, 62, 63, 64, 65, 67, 68, 69, 71, 73, 74, 75, 76, 77, 79, 80, 81, 83, 84, 85, 86, 87, 89, 90, 91, 92, 93, 94, 95
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| Complement of A006093 (primes minus 1); numbers which can be written as i*j+i+j, 0<i<=j: A072670(a(n))>0 for n>1; a(n)! is divisible by a(n)*(a(n)+1)/2, see A060462.
A072668 U A006093 = A000027. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Oct 22 2009]
|
|
|
FORMULA
| a(n) = A002808(n) - 1.
a(n)=2*A002808(n)-A079696(n). [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Oct 22 2009]
|
|
|
CROSSREFS
| Cf. A066938, A072672.
Cf. A000027, A006093, A079696. [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Oct 22 2009]
Sequence in context: A144724 A196990 A060462 * A062958 A184996 A153309
Adjacent sequences: A072665 A072666 A072667 * A072669 A072670 A072671
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Henry Bottomley (se16(AT)btinternet.com), Apr 11 2001
|
| |
|
|
