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A280943 Least number k such that sopfr(k) = sopfr(k + n), where sopfr(k) is the integer log of k. 1
5, 10, 7, 20, 7, 14, 20, 40, 13, 14, 21, 28, 14, 40, 19, 33, 11, 26, 56, 28, 49, 42, 115, 56, 35, 28, 31, 57, 11, 38, 50, 66, 63, 11, 17, 52, 11, 112, 42, 51, 22, 98, 11, 84, 57, 35, 52, 95, 138, 13, 33, 56, 22, 62, 77, 114, 61, 22, 39, 76, 44, 13, 91, 57, 70 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1000

EXAMPLE

a(1) = 5 because 5 is the least number such that sopfr(5) = sopfr(5 + 1) = 5 .

a(2) = 10 because 10 is the least number such that sopfr(10) = sopfr(10 + 2) = 7 .

MAPLE

with(numtheory):P:=proc(q) local a, b, k, n; for n from 1 to q do for k from 1 to q do

a:=ifactors(k)[2]; b:=ifactors(k+n)[2];

if add(a[k][1]*a[k][2], k=1..nops(a))=add(b[k][1]*b[k][2], k=1..nops(b))

then print(k); break; fi; od; od; end: P(10^9);

CROSSREFS

Cf. A001414, A065925.

Sequence in context: A185341 A067843 A245942 * A316707 A109360 A141622

Adjacent sequences:  A280940 A280941 A280942 * A280944 A280945 A280946

KEYWORD

nonn,easy

AUTHOR

Paolo P. Lava, Jan 11 2017

STATUS

approved

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Last modified February 17 02:33 EST 2019. Contains 320200 sequences. (Running on oeis4.)