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A163599 The smallest pronic (A002378) with the same most significant digits as n. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A303782 A335043 A040143 * A334700 A302799 A213059

Adjacent sequences:  A163596 A163597 A163598 * A163600 A163601 A163602

KEYWORD

nonn,base

AUTHOR

Claudio Meller, Aug 01 2009

STATUS

approved

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Last modified August 7 23:50 EDT 2022. Contains 355995 sequences. (Running on oeis4.)