

A027692


a(n) = n^2 + n + 7.


7



7, 9, 13, 19, 27, 37, 49, 63, 79, 97, 117, 139, 163, 189, 217, 247, 279, 313, 349, 387, 427, 469, 513, 559, 607, 657, 709, 763, 819, 877, 937, 999, 1063, 1129, 1197, 1267, 1339, 1413, 1489, 1567, 1647, 1729, 1813, 1899, 1987, 2077, 2169, 2263
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OFFSET

0,1


COMMENTS

Integers k for which the discriminant of x^3kxk is a square.  Jacob A. Siehler, Mar 14 2009
For n > 2: a(n) = A176271(n+1,4).  Reinhard Zumkeller, Apr 13 2010


LINKS

Muniru A Asiru, Table of n, a(n) for n = 0..3000
P. De Geest, Palindromic Quasi_Over_Squares of the form n^2+(n+X)
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

a(n) = 2*n + a(n1) (with a(0)=7).  Vincenzo Librandi, Aug 05 2010
G.f.: (7 + 12*x  7*x^2) / (x1)^3.  R. J. Mathar, Feb 06 2011
a(n+1) = n^2+3*n+9, see A005471.  R. J. Mathar, Jun 06 2019
a(n) mod 6 = A109007(n+2).  R. J. Mathar, Jun 06 2019


MAPLE

A027692 := proc(n)
n*(n+1)+7 ;
end proc: # R. J. Mathar, Jun 06 2019


MATHEMATICA

f[n_]:=n^2+n+7; f[Range[0, 60]] (* Vladimir Joseph Stephan Orlovsky, Feb 06 2011 *)


PROG

(PARI) a(n)=n^2+n+7 \\ Charles R Greathouse IV, Jun 11 2015
(GAP) List([0..50], n>n^2+n+7); # Muniru A Asiru, Jul 15 2018


CROSSREFS

Cf. A002522, A005471 (subset of primes).
Sequence in context: A129069 A258616 A125866 * A297063 A185720 A032487
Adjacent sequences: A027689 A027690 A027691 * A027693 A027694 A027695


KEYWORD

nonn,easy


AUTHOR

Patrick De Geest


STATUS

approved



