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A292774 a(n) = smallest m such that Sum_{i=1..m} 1/sqrt(prime(i)) >= n. 2
2, 4, 8, 13, 21, 30, 43, 58, 76, 97, 121, 149, 180, 214, 252, 294, 340, 390, 444, 502, 564, 630, 700, 775, 854, 937, 1025, 1118, 1215, 1317, 1423, 1535, 1650, 1771, 1897, 2027, 2162, 2303, 2448, 2598, 2753, 2914, 3079, 3250, 3426, 3607, 3793, 3984, 4181, 4383, 4591, 4803, 5022, 5245, 5474, 5709 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..500

FORMULA

a(n) ~ (n^2*log(n))/2. - Benoit Cloitre, Oct 01 2017 [This follows from the asymptotics for A292775]

MAPLE

Digits:=50;

s0:=0; k:=1; lisi:=[]; lisP:=[];

for i from 1 to 10000 do p:=ithprime(i);

s0:=s0+evalf(1/sqrt(p));

if s0 >= k then k:=k+1; lisi:=[op(lisi), i]; lisP:=[op(lisP), p]; fi;

od:

lisi; # A292774

lisP; # A292775

MATHEMATICA

f[n_]:=Block[{k=0, s=0}, While[s<n, k++; s=N[s+1/Sqrt[Prime[k]], 50]]; k]; Table[f[n], {n, 1, 60}] (* Vincenzo Librandi, Oct 01 2017 *)

CROSSREFS

Cf. A292775; A019529, A054040.

Sequence in context: A130840 A115266 A164508 * A026039 A004978 A005282

Adjacent sequences:  A292771 A292772 A292773 * A292775 A292776 A292777

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Sep 30 2017

STATUS

approved

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Last modified June 19 17:22 EDT 2018. Contains 305594 sequences. (Running on oeis4.)