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A342246 Numbers k such that k-1, k and k+1 are all composite with four, five and six (not necessarily distinct) prime factors respectively. 1
11151, 13455, 23375, 26271, 31311, 33776, 36125, 40375, 45495, 46375, 48411, 49049, 49167, 61335, 63125, 74151, 77895, 78111, 78351, 80271, 82575, 83511, 84591, 86031, 87375, 88749, 90207 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Dumitru Damian, Table of n, a(n) for n = 1..10456

EXAMPLE

For k=11151 we have 11150 = 2 * 5^2 * 223 which is composite with four prime factors, 11151 = 3^3 * 7 * 59 which is composite with five prime factors and 11152 = 2^4 * 17 * 41 which is composite with six prime factors.

PROG

(Sage)

# The following SageMath algorithm will generate all terms up to 100000

L=[]

for n in [1..100000]:

    sum1, sum2, sum3 = 0, 0, 0

    for f in list(factor(n)):

        sum1+=f[1]

    for f in list(factor(n+1)):

        sum2+=f[1]

    for f in list(factor(n+2)):

        sum3+=f[1]

    if sum1==4 and sum2==5:

        if sum3==6:

            L.append(n+1)

print(L)

(PARI) for(n=3, 100000, if(bigomega(n-1)==4&&bigomega(n)==5&&bigomega(n+1)==6, print1(n, ", "))) \\ Hugo Pfoertner, Mar 07 2021

CROSSREFS

Subsequence of A342258.

Cf. A001222, A014613, A014614, A046306.

Sequence in context: A205751 A205473 A250687 * A001727 A190793 A247925

Adjacent sequences:  A342243 A342244 A342245 * A342247 A342248 A342249

KEYWORD

nonn

AUTHOR

Sean Lestrange, Mar 07 2021

STATUS

approved

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Last modified May 27 12:49 EDT 2022. Contains 354097 sequences. (Running on oeis4.)