A125841 Numbers k such that previous_prime(k)=k-sd and next_prime(k)=k+sd where sd is sum of the distinct prime factors of k.

144, 288, 1728, 5184, 7168, 11760, 21632, 21952, 73500, 110592, 113400, 114244, 151263, 153790, 186624, 205800, 235298, 250563, 663552, 708588, 1404928, 2976750, 3449628, 4738500, 5265000, 7077888, 9437184, 11529602, 11745162

Offset

1,1

Comments

14267656658790241528591830756844692582808594415616 is a 50-digit term of this sequence. 493009335 is the smallest number k such that previous_prime(k)=k-s and next_prime(k)=k+s where s is sum of the prime factors of k. What is the next number with the same property?

Links

Table of n, a(n) for n=1..29.

Example

113400=2^3*3^4*5^2*7 is a term because previous_prime(113400)=113400-(2+3+5+7) and next_prime(113400)=113400+(2+3+5+7).

Mathematica

Do[If[c=Apply[Plus, PrimeFactorList[n]]; n-c==PreviousPrime[n]&&n+c== NextPrime[n], Print[n]], {n, 4, 20000000}]

Crossrefs

Cf. A008472, A125840.

Sequence in context: A250773 A262245 A134341 * A320457 A154051 A335543

Adjacent sequences: A125838 A125839 A125840 * A125842 A125843 A125844

Keyword

easy,nonn,base

Author

Farideh Firoozbakht, Feb 04 2007, corrected Feb 08 2007

Status

approved