

A123246


a(n) = PrimePi(n) + (1)^(PrimePi(n) + 1) (cf. A000720).


1



1, 2, 1, 1, 4, 4, 3, 3, 3, 3, 6, 6, 5, 5, 5, 5, 8, 8, 7, 7, 7, 7, 10, 10, 10, 10, 10, 10, 9, 9, 12, 12, 12, 12, 12, 12, 11, 11, 11, 11, 14, 14, 13, 13, 13, 13, 16, 16, 16, 16, 16, 16, 15, 15, 15, 15, 15, 15, 18, 18, 17, 17, 17, 17, 17, 17, 20, 20, 20, 20, 19, 19, 22, 22, 22, 22, 22, 22, 21, 21, 21, 21, 24, 24, 24, 24, 24, 24, 23, 23, 23, 23
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


REFERENCES

Lynn Arthur Steen and J. Arthur Seebach, Jr., Counterexamples in Topology, Dover, New York, 1978, page 134.


LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000


MATHEMATICA

f[n_] = PrimePi[n] + (1)^(PrimePi[n] + 1); Table[f[n], {n, 1, 200}]


PROG

(PARI) a(n) = primepi(n) + (1)^(primepi(n) + 1); \\ Michel Marcus, Oct 12 2018


CROSSREFS

Cf. A000720, A055670, A103889.
Sequence in context: A123521 A322115 A294217 * A122518 A129704 A144460
Adjacent sequences: A123243 A123244 A123245 * A123247 A123248 A123249


KEYWORD

sign


AUTHOR

Roger L. Bagula, Oct 07 2006


EXTENSIONS

Edited by N. J. A. Sloane, Oct 08 2006


STATUS

approved



