0,1

Continued fraction expansion of tanh(1/5). - Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 17 2002

n such that 5 divides the numerator of B(2n) where B(2n) = the 2n-th Bernoulli number. - Benoit Cloitre (benoit7848c(AT)orange.fr), Jan 01 2004

5 times odd numbers. - Omar E. Pol (info(AT)polprimos.com), May 02 2008

5th transversal numbers (or 5-transversal numbers): Numbers of the 5th column of positive numbers in the square array of nonnegative and polygonal numbers A139600. Also, numbers of the 5th column in the square array A057145. - Omar E. Pol (info(AT)polprimos.com), May 02 2008

Except for the first term, a(n)=20*n-a(n-1), (with a(1)=15) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 23 2009]

Tanya Khovanova, Recursive Sequences

a(n) = (A000217(5)-5)*n+5 = (15-5)n+5 = 10n+5 = 5(2n+1). - Omar E. Pol (info(AT)polprimos.com), May 02 2008

a(n) = A005408(n)*5. [From Omar E. Pol (info(AT)polprimos.com), Oct 19 2008]

For n=2, a(2)=20*2-15=25; n=3, a(3)=20*3-25=35; n=4, a(4)=20*4-35=45 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 23 2009]

(Other) sage: [i for i in range(450) if gcd(i, 20) == 5] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 20 2009]

(Other) sage: [i+5 for i in range(446) if gcd(i, 10) == 10] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 20 2009]

Cf. A000367.

Cf. A016957, A057145, A139600, A139606.

Subsequence of A034709, together with A017281, A017293, A139222, A139245, A139249, A139264, A139279 and A139280.

Cf. A005408. [From Omar E. Pol (info(AT)polprimos.com), Oct 19 2008]

Sequence in context: A043509 A121025 A031322 this_sequence A068528 A061443 A147495

Adjacent sequences: A017326 A017327 A017328 this_sequence A017330 A017331 A017332

nonn,easy

N. J. A. Sloane (njas(AT)research.att.com).