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 A115908 Numbers n such that phi(n) plus the n-th prime is a triangular number. 2
 1, 5, 6, 15, 23, 141, 150, 258, 317, 340, 359, 378, 471, 503, 768, 1363, 2175, 2516, 3285, 3342, 3815, 3905, 4385, 4748, 5385, 5976, 6026, 6900, 7048, 7151, 7411, 7698, 8251, 8310, 8828, 10182, 10461, 12022, 12508, 13722, 13840, 15456, 16582 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE phi(503)+prime(503)=4095=T(90). MATHEMATICA With[{trnos = Accumulate[Range[5000]]}, Select[Range[20000], MemberQ[trnos, (EulerPhi[#] + Prime[#])] &]] (* Harvey P. Dale, Jan 12 2011 *) PROG (PARI) isok(n) = ispolygonal(prime(n) + eulerphi(n), 3); \\ Michel Marcus, Jan 25 2014 CROSSREFS Cf. A115882, A115907. Sequence in context: A121847 A030533 A227066 * A247962 A241307 A185876 Adjacent sequences:  A115905 A115906 A115907 * A115909 A115910 A115911 KEYWORD nonn AUTHOR Giovanni Resta, Feb 06 2006 STATUS approved

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Last modified October 14 17:31 EDT 2019. Contains 328022 sequences. (Running on oeis4.)