This site is supported by donations to The OEIS Foundation.

 Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084419 a(n) = number of primes that can be formed by adding 1 to the product of any subset of the divisors of n. 2
 1, 2, 1, 3, 1, 6, 1, 4, 1, 4, 1, 11, 1, 4, 1, 5, 1, 10, 1, 9, 1, 3, 1, 19, 1, 4, 1, 7, 1, 26, 1, 5, 1, 2, 1, 25, 1, 2, 1, 14, 1, 25, 1, 6, 1, 3, 1, 30, 1, 6, 1, 6, 1, 16, 1, 12, 1, 3, 1, 81, 1, 2, 1, 6, 1, 18, 1, 5, 1, 18, 1, 41, 1, 4, 1, 3, 1, 22, 1, 20, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(2n-1) = 1. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..1000 EXAMPLE a(6) = 6: the divisors of 6 are 1, 2, 3 and 6 and the divisor products are 1, 2, 3, 6, 12, 18 and 36; the primes arising are 2, 3, 7, 13, 19 and 37. a(12) = 11 = #{2, 3, 5, 7, 13, 19, 37, 73, 97, 433, 577}. MATHEMATICA Table[Count[Union[Times@@@Subsets[Divisors[n], DivisorSigma[0, n]]]+1, _?PrimeQ], {n, 100}] (* Harvey P. Dale, Jun 24 2013 *) CROSSREFS Cf. A119607. Sequence in context: A152063 A321738 A022458 * A119606 A034850 A220377 Adjacent sequences:  A084416 A084417 A084418 * A084420 A084421 A084422 KEYWORD nonn AUTHOR Amarnath Murthy, Jun 01 2003 EXTENSIONS More terms from David Wasserman, Dec 28 2004 Corrected by Harvey P. Dale, Jun 24 2013 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 12 00:07 EST 2018. Contains 318052 sequences. (Running on oeis4.)