A065574 Numbers k such that the first k decimal digits < 6 of Pi, read as a base-6 number, form a prime.

1, 2, 4, 5, 52, 154, 219, 270, 2455

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Example

The digits of Pi less than 6 begins 3, 1, 4, 1, 5, 2, 5, 3, ..., interpreting increasing prefixes of these digits in base 6, we have 3_6 = 3 is prime (hence 1 is in the sequence), 31_6 = 19 is prime (hence 2 is in the sequence), 314_6 = 118 is not prime, 3141_6 = 709 is prime (hence 4 is in the sequence). - Sean A. Irvine, Sep 06 2023

Mathematica

p = First[ RealDigits[ Pi, 10, 10^5]];
p = p[[ Select[ Range[10^5], p[[#]] <= 5 & ]]];
Do[ If[ PrimeQ[ FromDigits[ Take[p, n], 6]], Print[n]], {n, 3000} ]

Crossrefs

Sequence in context: A210418 A167454 A056683 * A247963 A105288 A242915

Adjacent sequences: A065571 A065572 A065573 * A065575 A065576 A065577

Keyword

nonn,base,more,less

Author

Robert G. Wilson v, Dec 01 2001

Extensions

Data corrected by Sean A. Irvine, Sep 06 2023

Status

approved