A163599 The smallest pronic (A002378) with the same most significant digits as n.

12, 2, 30, 42, 56, 6, 72, 812, 90, 1056, 110, 12, 132, 1406, 156, 1640, 1722, 182, 1980, 20, 210, 2256, 2352, 240, 2550, 2652, 272, 2862, 2970, 30, 3192, 32220, 3306, 342, 3540, 3660, 3782, 380, 3906, 4032, 4160, 42, 43056, 4422, 4556, 462, 47306, 4830

Offset

1,1

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Maple

A002378 := proc(n) n*(n+1) ; end:
A163599 := proc(n) ndgs := convert(n, base, 10) ; for i from 1 do wrks := true ; prd := convert( A002378(i), base, 10) ; for d from 1 to nops(ndgs) do if op(-d, ndgs) <> op(-d, prd) then wrks := false; break; fi; od: if wrks then RETURN( A002378(i) ) ; fi; od: end:
seq(A163599(n), n=1..80) ; # R. J. Mathar, Aug 07 2009

Prog

(Python)
from sympy import isprime
def a(n):
    s, k = str(n), 1
    while not str(k*(k+1)).startswith(s): k += 1
    return k*(k+1)
print([a(n) for n in range(1, 49)]) # Michael S. Branicky, Dec 02 2021

Crossrefs

Sequence in context: A335043 A360287 A040143 * A334700 A302799 A213059

Adjacent sequences: A163596 A163597 A163598 * A163600 A163601 A163602

Keyword

nonn,base

Author

Claudio Meller, Aug 01 2009

Status

approved