A319626 -id:A319626 - cp's OEIS frontend

A342010 Number of times the term 2 has occurred so far in the range 1..n of A073751.

1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10

Offset: 1

Antti Karttunen, Mar 08 2021

nonn

Number of prime factors (with multiplicity) in the primorial deflation of the n-th colossally abundant number [A342012(n) = A319626(A004490(n))], provided that the quotient A004490(1+n)/A004490(n) is always a prime.

Amiram Eldar, Table of n, a(n) for n = 1..10000

Cf. A000120, A001222, A004490, A073751, A319626, A342012, A342013.

Block[{a = {2}, b, c, f, k, m, n, q = {1}, lim = 105}, f[w_] := Block[{p = w[[1]], i = w[[2]]}, ((Log[(p^(i + 2) - 1)/(p^(i + 1) - 1)])/Log[p]) - 1]; m = {{2, 1}, {3, 0}}; c = 1; b = Array[f[m[[#]]] &, c + 1]; For[n = 2, n <= lim, n++, k = Position[b, Max[b]][[1, 1]]; AppendTo[a, m[[k, 1]]]; AppendTo[q, Boole[m[[k, 1]] == 2]]; m[[k, 2]]++; If[k > c, c++; AppendTo[m, {Prime[k + 1], 0}]; AppendTo[b, f[m[[-1]]]]]; b[[k]] = f[m[[k]]]]; Accumulate@ q] (* Michael De Vlieger, Mar 12 2021, after T. D. Noe at A073751 *)

v073751 = readvec("b073751_to.txt"); \\ Prepared with gawk '{ print $2 }' < b073751.txt > b073751_to.txt
A073751(n) = v073751[n];
A342010(n) = sum(k=1,n,(2==A073751(k)));

a(n) = Sum_{k=1..n} [2==A073751(k)], where [ ] is the Iverson bracket.

a(n) = A001222(A342012(n)) = A000120(A342013(n)).

A346099 a(n) = gcd(n, A346098(n)).

Original entry on oeis.org

1, 2, 3, 4, 5, 3, 7, 1, 1, 5, 11, 3, 13, 7, 5, 1, 17, 1, 19, 5, 7, 11, 23, 3, 1, 13, 3, 7, 29, 5, 31, 2, 11, 17, 7, 1, 37, 19, 13, 1, 41, 1, 43, 11, 1, 23, 47, 1, 1, 1, 17, 13, 53, 9, 11, 7, 19, 29, 59, 1, 61, 31, 1, 4, 13, 11, 67, 17, 23, 1, 71, 3, 73, 37, 25, 19, 1, 13, 79, 1, 1, 41, 83, 1, 17, 43, 29, 11, 89

Offset: 1

Antti Karttunen, Jul 07 2021

nonn

Only powers of primes (A000961) occur as terms. A346100 lists the exponents.

Cf. A000961, A064989, A319626, A324886, A346095, A346096, A346097, A346098, A346100.

Cf. A346090 (positions of ones).

A064989(n) = { my(f = factor(n)); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f); };
A319626(n) = (n / gcd(n, A064989(n)));
A346099(n) = gcd(n, A064989(A319626(A324886(n)))); \\ Rest of program in A324886.

a(n) = gcd(n, A346098(n)) = gcd(n, A064989(A319626(A324886(n)))).

A387164 Numbers k for which gcd(k, A003961(k)) = gcd(sigma(k), A003961(k)), and that satisfy Euler's condition for odd perfect numbers (A228058).

Original entry on oeis.org

117, 153, 333, 369, 425, 477, 549, 637, 657, 845, 873, 909, 925, 1017, 1053, 1233, 1325, 1377, 1413, 1421, 1445, 1525, 1557, 1629, 1737, 1773, 1805, 1813, 1825, 2009, 2097, 2169, 2225, 2313, 2493, 2525, 2529, 2597, 2637, 2725, 2817, 2825, 2853, 2989, 2997, 3033, 3177, 3321, 3357, 3425, 3509, 3573, 3577, 3609, 3725

Offset: 1

Antti Karttunen, Aug 28 2025

Terms k of A228058 for which A322361(k) = A342671(k), or equally, such that A319626(k) = A349164(k).

Intersection of A228058 and A349174.
Union of A387166 and A387167.
Differs from its subsequence A387167 for the first time at n=201, where a(201) = 14157, while A387167(201) = 14225.
Cf. A000203, A003961, A319626, A322361, A342671, A349164.
Cf. also A371082.

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA228058(n) = if(!(n%2)||(omega(n)<2), 0, my(f=factor(n), y=0); for(i=1, #f~, if(1==(f[i, 2]%4), if((1==y)||(1!=(f[i, 1]%4)), return(0), y=1), if(f[i, 2]%2, return(0)))); (y));
isA349174(n) = if(!(n%2), 0, my(u=A003961(n)); gcd(u, sigma(n))==gcd(u, n));
isA387164(n) = (isA228058(n) && isA349174(n));

A349177 Odd numbers k for which gcd(k, A003961(k)) = gcd(sigma(k), A003961(k)) = 1, where A003961(n) is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors function.

Original entry on oeis.org

1, 3, 5, 7, 9, 11, 13, 17, 19, 21, 23, 25, 29, 31, 33, 37, 39, 41, 43, 47, 49, 51, 53, 55, 59, 61, 63, 67, 69, 71, 73, 79, 81, 83, 85, 89, 91, 93, 95, 97, 101, 103, 107, 109, 111, 113, 115, 117, 119, 121, 123, 125, 127, 129, 131, 133, 137, 139, 141, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 167, 169, 173

Offset: 1

Antti Karttunen, Nov 11 2021

nonn

Odd numbers k for which k and A003961(k) are relatively prime, and also sigma(k) and A003961(k) are coprime.

Subsequence of A349174 from this first differs by not having term 135 (see A349176).
Intersection of A319630 and A349174, or equally, intersection of A349165 and A349174.
Cf. A000203, A003961, A319626, A348994, A349161, A349164, A349169.

Select[Range[1, 173, 2], GCD[#1, #3] == GCD[#2, #3] == 1 & @@ {#, DivisorSigma[1, #], Times @@ Map[NextPrime[#1]^#2 & @@ # &, FactorInteger[#]]} &] (* Michael De Vlieger, Nov 11 2021 *)

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA349177(n) = if(!(n%2),0,my(u=A003961(n),t=gcd(u,n)); (1==t)&&(gcd(u,sigma(n))==t));

A366876 Lexicographically earliest infinite sequence such that a(i) = a(j) => A337376(i) = A337376(j) for all i, j >= 0, where A337376 is the primorial deflation (numerator) of Doudna sequence.

Original entry on oeis.org

1, 2, 3, 4, 5, 3, 6, 7, 8, 9, 5, 10, 11, 6, 12, 13, 14, 15, 16, 17, 8, 5, 18, 19, 20, 21, 11, 6, 22, 12, 23, 24, 25, 26, 27, 28, 29, 16, 30, 31, 14, 15, 8, 9, 32, 18, 33, 34, 35, 36, 37, 38, 20, 11, 11, 39, 40, 41, 22, 12, 42, 23, 43, 44, 45, 46, 47, 48, 49, 27, 50, 51, 52, 53, 29, 54, 55, 30, 56, 57, 25, 26, 27, 28, 14

Offset: 0

Antti Karttunen, Oct 26 2023

nonn

Restricted growth sequence transform of A337376.

Antti Karttunen, Table of n, a(n) for n = 0..65537
Index entries for sequences related to binary expansion of n

Cf. A005940, A064989, A319626, A337376.

Cf. also A366877.

up_to = 65537;
rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om,invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om,invec[i],i); outvec[i] = u; u++ )); outvec; };
A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); (t); };
A064989(n) = {my(f); f = factor(n); if((n>1 && f[1,1]==2), f[1,2] = 0); for (i=1, #f~, f[i,1] = precprime(f[i,1]-1)); factorback(f)};
A319626(n) = (n / gcd(n, A064989(n)));
A337376(n) = A319626(A005940(1+n));
v366876 = rgs_transform(vector(1+up_to,n,A337376(n-1)));
A366876(n) = v366876[1+n];

A349175 Odd numbers k for which gcd(k, A003961(k)) <> gcd(sigma(k), A003961(k)), where A003961(n) is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors function.

Original entry on oeis.org

15, 27, 35, 45, 57, 65, 75, 77, 87, 99, 105, 143, 165, 171, 175, 177, 189, 195, 205, 221, 225, 231, 237, 245, 255, 261, 267, 297, 301, 315, 323, 325, 327, 345, 351, 375, 385, 399, 405, 415, 417, 429, 437, 447, 459, 465, 485, 495, 513, 525, 531, 537, 539, 555, 567, 585, 595, 597, 605, 609, 615, 621, 627, 629, 645

Offset: 1

Antti Karttunen, Nov 10 2021

nonn

Odd numbers for which A348994(n) <> A349161(n).

Equally, odd numbers such that A319626(n) <> A349164(n).

Cf. A000203, A003961, A319626, A348994, A349161, A349164.

Cf. A349169, A349174 (complement among the odd numbers).

Select[Range[1, 645, 2], GCD[#1, #3] != GCD[#2, #3] & @@ {#, DivisorSigma[1, #], Times @@ Map[NextPrime[#1]^#2 & @@ # &, FactorInteger[#]]} &] (* Michael De Vlieger, Nov 11 2021 *)

A003961(n) = { my(f = factor(n)); for (i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
isA349175(n) = if(!(n%2),0,my(u=A003961(n)); gcd(u,sigma(n))!=gcd(u,n));

cp's OEIS Frontend

A342010 Number of times the term 2 has occurred so far in the range 1..n of A073751.

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A346099 a(n) = gcd(n, A346098(n)).

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A387164 Numbers k for which gcd(k, A003961(k)) = gcd(sigma(k), A003961(k)), and that satisfy Euler's condition for odd perfect numbers (A228058).

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A349177 Odd numbers k for which gcd(k, A003961(k)) = gcd(sigma(k), A003961(k)) = 1, where A003961(n) is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors function.

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A366876 Lexicographically earliest infinite sequence such that a(i) = a(j) => A337376(i) = A337376(j) for all i, j >= 0, where A337376 is the primorial deflation (numerator) of Doudna sequence.

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A349175 Odd numbers k for which gcd(k, A003961(k)) <> gcd(sigma(k), A003961(k)), where A003961(n) is fully multiplicative with a(prime(k)) = prime(k+1), and sigma is the sum of divisors function.

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