A046519 Least n-digit 'happy' prime.

7, 13, 103, 1009, 10009, 100003, 1000003, 10000121, 100000039, 1000000009, 10000000033, 100000000003, 1000000000039, 10000000000411, 100000000000067, 1000000000000487, 10000000000000481, 100000000000000003

Offset

1,1

Comments

Values found by Harvey Heinz and Jud McCranie.

References

R. K. Guy, Unsolved Problems Number Theory, Sect. E34.

Links

Bo Gyu Jeong, Table of n, a(n) for n = 1..50

C. Rivera, Related puzzle page

Eric Weisstein's World of Mathematics, Happy Number

Prog

(Python)
from sympy import nextprime
def A046519(n):
    m = 10**(n-1)
    while (m:=nextprime(m)):
        k = m
        while k not in {1, 37, 58, 89, 145, 42, 20, 4, 16}:
            k = sum((0, 1, 4, 9, 16, 25, 36, 49, 64, 81)[ord(d)-48] for d in str(k))
        if k == 1:
            return m # Chai Wah Wu, Aug 02 2023

Crossrefs

Cf. A007770, A035497.

Sequence in context: A136720 A323468 A035030 * A283920 A128351 A192894

Adjacent sequences: A046516 A046517 A046518 * A046520 A046521 A046522

Keyword

nonn,base

Author

Patrick De Geest, Sep 15 1998

Status

approved