A055009 Smallest composite number x such that sigma(x + prime(n)#) = sigma(x) + prime(n)#, where prime(n)# = A002110(n) and sigma is A000203.

434, 104, 44, 176, 2924, 34256, 83509, 539081, 254963216, 14600541172, 201346999808

Offset

1,1

Comments

a(12) <= 14841476269604. a(13) <= 314064788156864. - Donovan Johnson, Mar 17 2013

Links

Table of n, a(n) for n=1..11.

Example

a(7) = 83509 = 37*37*61, sigma(83509)+510510 = 87234+510510 = sigma(83509+510510) = sigma(594019) = 597744.

Prog

(PARI) a(n)=my(P=prod(i=1, n, prime(i)), x=4); while(isprime(x) || sigma(x+P) != sigma(x)+P, x++); x \\ Charles R Greathouse IV, Feb 14 2013

Crossrefs

The prime solutions for particular sigma(x+primorial) = sigma(x)+primorial equations are in A049481-A049485.

A000203, A002110, A015913-A015917, A049902-A049905, A049481-A049485.

Sequence in context: A198450 A241925 A108832 * A054982 A108785 A219033

Adjacent sequences: A055006 A055007 A055008 * A055010 A055011 A055012

Keyword

more,nonn

Author

Labos Elemer, May 31 2000

Extensions

a(9)-a(10) from Donovan Johnson, Oct 15 2008

a(11) from Donovan Johnson, Mar 08 2013

Status

approved