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A026478 a(n) = least positive integer > a(n-1) and not of form a(i)*a(j)*a(k) for 1<=i<=j<=k<n. +0
1
1, 2, 3, 5, 7, 11, 13, 16, 17, 19, 23, 24, 29, 31, 36, 37, 40, 41, 43, 47, 53, 54, 56, 59, 60, 61, 67, 71, 73, 79, 81, 83, 84, 88, 89, 90, 97, 100, 101, 103, 104, 107, 109, 113, 126, 127, 128, 131, 132, 135, 136, 137, 139, 140, 149, 150, 151, 152, 156, 157, 163, 167 (list; graph; listen)
OFFSET

1,2

COMMENT

Number of repeated prime divisors of n is a square. - Jason Earls (zevi_35711(AT)yahoo.com), Jul 01 2001

FORMULA

1 together with numbers with 3m+1 prime factors (for some m >= 0).

PROGRAM

(PARI) v=[]; for(n=1, 150, v=concat(v, if(issquare(bigomega(n)), n))); v (ignore the zeros)

CROSSREFS

Cf. A016777 and A001222.

Sequence in context: A117093 A062063 A167175 this_sequence A154893 A084111 A020625

Adjacent sequences: A026475 A026476 A026477 this_sequence A026479 A026480 A026481

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

EXTENSIONS

Formula from Henry Bottomley (se16(AT)btinternet.com), Feb 09 2000. Definition corrected by and more terms from Larry Reeves (larryr(AT)acm.org), Mar 24 2000.

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Last modified December 1 19:22 EST 2009. Contains 167811 sequences.


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