The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation. Please make a donation to keep the OEIS running. We are now in our 56th year. In the past year we added 10000 new sequences and reached almost 9000 citations (which often say "discovered thanks to the OEIS"). Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A212154 (A212153(n)^3 + 1)/7^n, n >= 0. 3
 1, 18, 140, 20, 479393, 219600095, 4804461081, 686351583, 6679631931865, 82080661415031, 8898622841908566, 174149720118385232, 7290250572352382182, 65315972853762054047, 98713213404986046050649 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) is integer because A212153(n) is one of the three solutions of X(n)^3+1 == 0 (mod 7^n), namely the one satisfying also X(n) == 5 (mod 7). See the comments on A210853, and the Nagell reference given in A210848. LINKS FORMULA a(n) = (b(n)^3+1)/7^n, n>=0, with b(n):=A212153(n) given by a recurrence. See also a Maple program for b(n) there. EXAMPLE a(0) = 1/1 = 1. a(3) = (19^3 + 1)/7^3 = 6860/343  = 20, (b(3) = 19^7 (mod 7^3) = 19). CROSSREFS Cf.  A210848, A210849 (the p=5 case). A210853, A212156. Sequence in context: A114239 A087115 A163707 * A108680 A204273 A081074 Adjacent sequences:  A212151 A212152 A212153 * A212155 A212156 A212157 KEYWORD nonn,easy AUTHOR Wolfdieter Lang, May 02 2012 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 November 26 12:37 EST 2020. Contains 338639 sequences. (Running on oeis4.)