A066490 - OEIS

A066490

Number of primes of the form 4m+3 that are <= n.

0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 13, 13, 13

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OFFSET

1,7

COMMENTS

Partial sums of A079261. - Reinhard Zumkeller, Feb 06 2014

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

FORMULA

A066339(n) + a(n) = A000720(n) - 1 for n >= 2. - Jianing Song, Apr 28 2021

MATHEMATICA

Table[ Length[ Select[ Union[ Table[ Prime[ PrimePi[i]], {i, 2, n}]], Mod[ #, 4] == 3 & ]], {n, 2, 100} ]

Accumulate[Table[If[PrimeQ[n]&&Mod[n, 4]==3, 1, 0], {n, 100}]] (* Harvey P. Dale, Mar 17 2021 *)

PROG

(PARI) for(n=1, 100, print1(sum(i=1, n, if((i*isprime(i)-3)%4, 0, 1)), ", "))

(Haskell)

a066490 n = a066490_list !! (n-1)

a066490_list = scanl1 (+) $ map a079261 [1..]

-- Reinhard Zumkeller, Feb 06 2014

CROSSREFS

Cf. A000720, A066339, A296020.

Sequence in context: A124156 A324965 A072749 * A156685 A124230 A330780

Adjacent sequences: A066487 A066488 A066489 * A066491 A066492 A066493

KEYWORD

easy,nonn

AUTHOR

Robert G. Wilson v, Jan 03 2002

STATUS

approved

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