A089787 a(4n-3), a(4n-2), a(4n-1), and a(4n) are the units digit of the n-th prime followed by 1, 3, 7, and 9 respectively.

21, 23, 27, 29, 31, 33, 37, 39, 51, 53, 57, 59, 71, 73, 77, 79, 11, 13, 17, 19, 31, 33, 37, 39, 71, 73, 77, 79, 91, 93, 97, 99, 31, 33, 37, 39, 91, 93, 97, 99, 11, 13, 17, 19, 71, 73, 77, 79, 11, 13, 17, 19, 31, 33, 37, 39, 71, 73, 77, 79, 31, 33, 37, 39, 91, 93, 97, 99, 11

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = 5+(-1)^n+3*cos(n*Pi/2)-3*sin(n*Pi/2)+10*(prime(floor((n+3)/4)) mod 10). - Wesley Ivan Hurt, May 06 2021

Mathematica

Flatten[Table[Mod[Prime[n], 10]*10+{1, 3, 7, 9}, {n, 1, 50}]]
a[n_] := Mod[Prime[Floor[(n + 3)/4]], 10]*10 + {1, 3, 7,
9}[[Mod[n - 1, 4] + 1]] (* Charles R Greathouse IV, Jan 02 2013 *)
Table[10*Mod[Prime[n], 10]+{1, 3, 7, 9}, {n, 30}]//Flatten (* Harvey P. Dale, Aug 24 2019 *)

Prog

(PARI) a(n)=prime((n+3)\4)%10*10+[9, 1, 3, 7][n%4+1] \\ Charles R Greathouse IV, Jan 02 2013

Crossrefs

Cf. A007652, A131712.

Cf. A089784 (essentially the same).

Sequence in context: A095441 A095437 A366202 * A329914 A229221 A157676

Adjacent sequences: A089784 A089785 A089786 * A089788 A089789 A089790

Keyword

nonn,easy,less

Author

Roger L. Bagula, Jan 09 2004

Status

approved