The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A237640 Numbers n of the form p^5 - Phi_5(p) (for prime p) such that n^5 - Phi_5(n) is also prime. 1
 122, 340352, 830519696, 11479086422, 266390469692, 310503441398, 2718130415306, 14837993872846, 59538248604388, 889257663626476, 2496623039993996, 6427431330617746, 7120028814392596, 10777302002014868, 12942591289426088, 24039736320940828 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All numbers are congruent to 2 mod 10, 6 mod 10, or 8 mod 10. x^5 - Phi_5(x) = x^5-x^4-x^3-x^2-x-1. LINKS EXAMPLE 122 = 3^5-3^4-3^3-3^2-3^1-1 (3 is prime) and 122^5-122^4-122^3-122^2-122^1-1 = 26803717321 is prime. Thus, 122 is a member of this sequence. PROG (Python) import sympy from sympy import isprime def poly5(x): ..if isprime(x): ....f = x**5-x**4-x**3-x**2-x-1 ....if isprime(f**5-f**4-f**3-f**2-f-1): ......return True ..return False x = 1 while x < 10**5: ..if poly5(x): ....print(x**5-x**4-x**3-x**2-x-1) ..x += 1 CROSSREFS Cf. A125083, A237527, A237528, A237639. Sequence in context: A208397 A098129 A198603 * A258489 A015079 A015042 Adjacent sequences:  A237637 A237638 A237639 * A237641 A237642 A237643 KEYWORD nonn AUTHOR Derek Orr, Feb 10 2014 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 June 18 20:45 EDT 2021. Contains 345121 sequences. (Running on oeis4.)